AUXILILARY-2014-2015

AUXILARY – PHYSICS - SESSION 2014 – 2015

INDEX (Main Experiments)

Expt No.

Date of performance

Name of the experiment Page No

Date of completion

Sign

E-1 (E) Ohm’s law – Resistance per unit length

2

E-2 (E) Metre Bridge – Resistance and resistivity

7

E-3 (E) Metre Bridge – Combination of resistances

9

E-4 (E) Potentiometer – Comparison of EMF

15

E-5 (E) Potentiometer – Internal resistance of a cell

16

E-6(E) Galvanometer – Resistance and Figure of merit

21

E-7(E) Conversion of Galvanometer into Ammeter and Voltmeter

24

O-1(O) Prism – Angle of minimum deviation and refractive index

4

O-2 (O) Focal length of Convex Lens

11

O-3 (O) Focal Length of Concave Mirror

18

O-4 (O) I-V characteristics of p-n junction diode

27

O-5 (O) I – V characteristics of Zener diode

30

O-6 (O) Refractive index of a colour using glass slab

32

O-7 (O) Refractive index of a liquid using concave mirror

35

O-8 (O) I – V characteristics of a transistor

36

Any two Main experiments are to be performed during examination. One of them is from E and one

from O. “O” – Experiments are based on Optics (8 experiments). “E” – Experiments are based on

Electricity (7 experiments)

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Auxilary Notebook Preapared By: Dr. Pramada Lele 1 | P a g e

Resistance wire

Voltmeter

Ammeter Battery

One way key

Rheostat

Date: Experiment: E - Ohm’s law – Resistance per unit length

Aim: To determine resistance per cm of a given wire by plotting a graph of potential difference versus current.

Apparatus: A resistance wire, voltmeter, ammeter, one way key, rheostat, metre scale, battery eliminator, connecting wires and a piece of sand paper.

Circuit diagram:

- +

+ +

- -

How to connect: (To understand how to read the circuit diagram. NOT TO BE DRAWN IN THE FILE. ONLY FOR YOUR UNDERSTANDING)

voltmeter

- +

resistance + supply - key

rheostat

+ -

fixed variable

Ammeter

Formula used: R = V / I (Ω)

R = resistance of the coil, V = voltage across the resistance coil and I = current flowing through the resistance coil

Least Count = number of divisions / range of scale

Observations:


V

A

V

A

Range of ammeter: ---- to ------- A Least count of ammeter: -------- A

Range of voltmeter: ------- to ------- V Least count of voltmeter: ---------- V

Length of the given wire: --------- cm = --------- m

Zero error and zero correction:

1) Zero error of the ammeter (e1): --------- A 2) Zero correction of the ammeter (- e1): ----------- A

2) Zero error of the voltmeter (e2): --------- V 3)Zero correction of the voltmeter (-e2): -------- V

Observation table:

** n1 and n2 are the number of divisions in the voltmeter and ammeter respectively.

Sr. No.

Voltmeter reading Ammeter reading

Resistance R = (V / I) Ω

Voltmeter reading observed V (V)n1 x LC

Voltmeter reading corrected V [(n1 x LC) + (-e2)] (V)

Ammeter reading observed I (A)n2 x LC

Ammeter reading corrected I [(n2 x LC) + (-e1)] (A)

1

2

3

4

5

Average resistance of the wire = R = ---------- Ω

Graph: Y axis – Current (A) X axis – Voltage (V)

(Write scale for X as well as Y axis on the top of the graph)

Nature of the graph: Irrespective of position of various points plotted, an average straight line passing through the origin.

I (A) Slope of the graph = (Y2 – Y1) / (X2 – X1)

= I / V = 1 / R’

Resistance from the graph = 1 / slope

V(V) R’ = ------ Ω

Result:


1) Resistance per unit length = Average resistance of the wire from the observations / length of wire in m = R / l Ω m-1 = ---------- Ω m-1 = ---------- Ω cm-1

2) The graph between V and I is a straight line.

3) The given conductor is an ohmic conductor.

Precautions:

1) The connections should be neat, clean and tight.

2) Thick copper wires should be used for the connections after removing the insulation coating near the ends by rubbing it with sand paper.

3) Voltmeter and ammeter should be of proper range.

4) A low resistance rheostat should be used.

5) A key should be inserted only while taking observations to avoid heating of resistance (otherwise its resistance will increase)

Sources of error:

1) The instrument screws may be loose.

2) Thick connecting wires may not be available.

3) Rheostat may have high resistance.

Procedure:

1) Arrange the apparatus as per the diagram.

2) Clean the tips of the connecting wires with the help of sand paper.

3) Connect the circuit as per the circuit diagram.

4) Note down the range and least count of the ammeter and the voltmeter.

5) Insert the key and check for the functioning of the ammeter and voltmeter.

6) Note down the readings for V and I.

7) For the next reading, slightly change the position of the rheostat to get the different current in the circuit. Note down the reading from ammeter and voltmeter.

8) Repeat the procedure for noting down the next observations.

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Date: Experiment: O – Prism – Angle of minimum deviation and refractive index

Aim: To determine angle of minimum deviation for a given prism by plotting a graph between angle of incidence and angle of deviation and hence find the refractive index of glass prism.

Apparatus: Drawing board, white sheet of paper, prism, drawing pins, hall pins, pencil, protractor.


Diagram:

i = angle of incidencee = angle of emergenceA = angle of prism = 60o

δ = angle of deviationFormula used:μ = sin {[A+δm] / 2} / {sin [A / 2]}

Experimental set up:

(OBSERVATION SHEETS NEED TO BE PASTED IN THE FILE WITH APPROPRIATE DIRECTION OF THE RAYS)

Observation

table:

Sr No. Angle of incidence (io) Angle of deviation (o)

1

2

3

4

5

Angle of minimum deviation = δm = ------ (o)

Graph:

Y axis – angle of deviation X axis – angle of incidence

(Write scale for X as well as Y axis on the top of the graph)

Nature: Irrespective of position of various points, draw an average smooth line.


δ (o) On x- axis:

Origin: at 30o, then 1 sq = 5o angle of incidence

On Y: axis:

m Origin: at 30o, then 1 sq = ---- o of angle of deviation

i (o) * * * Select appropriate scale to draw full page graph

Calculations:

μ = sin {[A + δm] / 2} / {sin [A / 2]} = sin {( 60 + ------) / 2} / sin 30

= 2 sin (------) ** Use logarithmic table to find the value of sin (---)

= ------- (no unit)

Result:

1) Angle of minimum deviation is found to be: ------ o

2) Refractive index of prism =

Precautions:

1) The angle of incidence should lie between 35o – 60o

2) The pins should be fixed vertical.

3) The distance between the two pins placed on incident ray should not be less than 5 cm.

4) Arrow heads should be marked to represent the incident and emergent rays.

5) The same angle of prism should be used for all the observations.

Sources of error:

1) Pin pricks may be thick.

2) Measurement of angles may be wrong.

3) The distance between the two pins on incident ray might be less than 5 cm.

Procedure:

1) Place the given paper horizontally.

2) Draw a horizontal line at the centre of the paper from one end to another end.

3) Place the prism correctly on the horizontal line and draw the outline for the same at six different places.

4) Draw normal to the prism and then make angle of incidence for each prism ranging from 35o with the difference of 5o angle.


5) Draw the incident ray, show the arrow head pointing towards the prism.

6) Place the prism on the border line and pierce two pins on the incident ray such that the distance between the two is greater than 5 cm.

7) Try to look into the prism through the right hand surface of the prism for the image of the pins.

8) Pierce the next two pins at emergent side such that the tip of these pins is in a straight line with respect to the tip of earlier pins.

9) Draw an emergent line passing through the holes made by the two hall pins while tracing the emergent line. Show the arrow head pointing away from the prism.

10) Repeat the procedure for the rest of the angles.

11) The angle of deviation first decreases, reaches to the minimum and then increases.

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Date: Experiment: E - Metre Bridge – Resistance and resistivity

Aim: To find resistance of a given wire using metre bridge and hence determine the specific resistance of its material.

Apparatus: A metre bridge, Leclanche cell, a galvanometer, a jockey, one way key, screw gauge, metre scale, resistance box, a constantan wire, connecting wires, a piece of sand paper.

Diagram:

Formula:

Q = {(100 – l) / (l)} x P = working formula to find unknown resistance R = ρ (l / A) = resistance of the given wire ρ = R (A / l) = resistivity of the given wire A = Π r2 = area of the given wire


R. Box wire

Observations:

Table I: Length of the given wire = 100 cm = 1 m

Least count of the scale = -------- cmSr. No. Resistance from

resistance box P (Ω)

Balancing length from left hand side l (cm) (R)

Balancing length from right hand side (100 – l) (cm) (S)

Unknown resistance Q = {(100 – l) / (l)} x R (Ω)

1

2

3

4

5

Mean unknown resistance = (Q) ---------- Ω

Table II:

Least count (LC) of screw gauge = --------- mm

Zero error (e): ------ mm Corrected error (-e): --------- mm

Sr. No.

Main scale reading (mm) MSR

Circular scale reading CSR

(n)

Total reading TR = MSR + (n x LC) (mm)

Corrected reading (TR– e) (mm)

1

2

Mean diameter of the given constantan wire = ----------- mm = --------- x 10-3 mRadius of the given constantan wire = ----------- mResult:

1) Mean resistance of the given constantan wire = ----------- Ω

2) Area of the given wire = -------- m2

3) Observed value of the resistivity (ρ) of the given constantan wire = ---------- Ω m

Precautions:

1. The connections should be neat, clean and tight.

2. All the plugs in the resistance box should be tight.

3. Move the jockey gently over the bridge wire and do not rub it.

4. The plug in key K should be inserted only when the observations are to be taken.

5. Null point should be brought between 45 cm and 55 cm.

6. The wire should not make a loop.


Sources of error:

1. The instrument screws may be loose.

2. The plugs may not be clean.

3. The wire may not have uniform thickness.

4. The screw gauge may have faults like back lash error and wrong pitch.

Procedure:

1. Arrange the apparatus according to the diagram.

2. Make the connections as shown in the diagram after cleaning the ends of the wires with the help of a sand paper.

3. Plug the key, take out some resistance from the resistance box. Touch the jockey on the wire and check whether the deflection is observed on both the sides in the galvanometer after touching at the extreme ends of the metre bridge.

4. If the deflection is not coming on both the sides, then call the teacher. Otherwise, adjust the resistance from the resistance box so that the balancing length (null point) will be between 40 cm to 60 cm. Note this position as “l”.

--------------------------------------------------------------------------------------------------------------Date: Experiment: E - Metre Bridge – Combination of resistances

Aim: To verify the laws of combination (series and parallel) of resistances using a metre bridge.

Apparatus: A metre bridge, Leclanche cell, a galvanometer, a jockey, one way key, screw gauge, metre scale, resistance box, two resistance coils of known resistances, connecting wires, a piece of sand paper.

Diagram:

Formula used:

1) Q = {(100 – l) / (100)} x P 2) Rs (series) = R1 + R2

3) Rp (parallel) = (R1 x R2) / (R1 + R2) 4) Percentage error = {(Rs – R’s) / R’s} x 100

5) Percentage error = {(Rp – R’p) / R’p} x 100

where Rs and Rp are the theoretical values of the respective combination and R’s and R’p are the experimental values for the series and parallel combination respectively.


R. BoxCombination of resistances

** R1 and R2 are the magnitudes of individual resistances which you need to find it first by using the metre bridge only. Do not believe the magnitude written on it.

Observation Table:

Sr. No.

Description

Resistance from

resistance box R

(Ω)

Balancing length at left hand

side l (cm)

Balancing length at

right hand side (100 – l) (cm)

Unknown resistance S =

(100 – l) x R / (l) (Ω)

Resistance S (Ω)

Mean resistanc

e (Ω)

1

R1

R1 =

2

3

R2

R2 =

4

5R1 and R2

in series

R’s =

6

7R1 and R2

in parallel

R’p =

8

Calculations:

1) Theoretical Magnitude of the combination (series) of resistances = Rs = R1 + R2 = ------- Ω

2) Theoretical Magnitude of the combination (parallel) of resistances

= Rp = R1 R2 / (R1+R2) = ------- / ---------- = --------- Ω

3) Percentage error in series combination = {(Rs – R’s) / RS} x 100

= ------- / ------ = --------- %

4) Percentage error in parallel combination = {(Rp – R’p) / Rp} x 100

= ------ / -------- = --------- %

Result:

1) Magnitude of the first resistance = R1 = ----- Ω

2) Magnitude of the second resistance = R2 = ----- Ω

3) Experimental Magnitude of the combination (series) of resistances = R’s = ------- Ω

4) Experimental Magnitude of the combination (parallel) of resistances = R’p = ------- Ω


5) Theoretical Magnitude of the combination (series) of resistances = Rs = R1 + R2 = ------- Ω

6) Theoretical Magnitude of the combination (parallel) of resistances = R’p

= R1 R2/( R1+R2) = ------- Ω

7) Percentage error in series combination = ------- %

8) Percentage error in parallel combination = -------- %

Precautions:


2. All the plugs in the resistance box should be tight.

3. Move the jockey gently over the bridge wire and do not rub it.

4. The plug in key K should be inserted only when the observations are to be taken.

5. Null point should be brought between 45 cm and 55 cm. Otherwise adjust the resistance from the resistance box or check the emf of the cell.

6. The wire should not make a loop.

Sources of error:

1. The instrument screws may be loose.

2. The plugs may not be clean.

3. The wire may not have uniform thickness.

4. The screw gauge may have faults like back lash error and wrong pitch.

Procedure:

1. Arrange the apparatus according to the diagram.

2. Make the connections as shown in the diagram after cleaning the ends of the wires with the help of a sand paper.

3. Plug the key, take out some resistance from the resistance box. Touch the jockey on the wire and check whether the deflection is observed on both the sides in the galvanometer after touching at the extreme ends of the metre bridge.

4. If the deflection is not coming on both the sides, then call the teacher. Otherwise, adjust the resistance from the resistance box so that the balancing length (null point) will be between 40 cm to 60 cm. Note this position as “l”.

5. Take at least two readings per set.

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Date: Experiment: O – Focal length of Convex Lens

Aim: To find the focal length of a convex lens by plotting graphs between u and v or between 1/u and 1/v.

Apparatus: Convex lens, lens holder, two needles, screen, optical bench, knitting needle, half metre scale

Diagram: ray diagram for convex lens

Formula used: 1 / f = (1 / v) – (1 / u)

f = focal length of the lens, v = image distance, - u = object distance

Observations:

1. Approximate focal length of the given lens = ---------- cm

2. For index error:

Observed length of the given knitting needle = x = ---------- cm

Observed distance between the object needle and the lens when knitting needle is placed between them = y = ------ cm

Index error for u = e1 = (y – x) = -------- cm

Index correction for u = - e1 = (x – y) ------- cm

Observed distance between the image needle and the lens when knitting needle is placed between them = z = ------ cm

Index error for v = e2 = (z – x) = -------- cm

Index correction for u = - e2 = (x – z) = ------- cm


Convex lens

Observation table:

Position of Object Distance - u (cm)

Image Distance + v (cm)

- 1/u cm-1

+ 1/v cm-1Sr.

No.

Lens at O (cm)

Object needle at

A (cm)

Image needle at

C (cm)

Observed (O - A) = u' (cm)

Corrected u = u' + (-e1) (cm)

Observed (C - O) = v' (cm)

Corrected v = v' + (-e2) (cm)

1 50

2 50

3 50

4 50

5 50

Graphs:

1. – 1/u versus 1/v + (1/v)

Scale: cm-1

X – axis: 1 sq = 0.01 cm-1

Y – axis: 1 sq = 0.01 cm-1

- (1/u) cm-1 1/f (0,0)

2. – u versus + v v (cm)

(2f, 2f)

- u (cm) (0,0)

Calculations: (for any one of the readings)

1/f = 1/v – 1/u = 1/(-------------) – 1/(- ----------------)

= 1/(-------------) + 1/(----------------)

= 1 / -------- cm-1 f = -------- cm

Result:

1. Observed rough focal length of the given convex lens = ----------- cm

2. Focal length of the given convex lens by using formula = --------- cm


* Origin needs to be (0,0)

Break is not permitted

* Scale along x – axis as well as y – axis must be same

* Select the scale in such a way so that when a straight line is drawn, you can find the intercepts along x – axis as well as y – axis.

* * Origin needs to be (0,0), without break

Scale along x – axis as well as y – axis must be same = 1 sq = 5 cm

* Select the scale in such a way so that you can find the intercepts if you draw a straight line at 45o from origin, it gives the coordinates of (2f, 2f)

45o

3. Focal length of the given convex lens by using (- 1/u) versus (+ 1/v) graph = ------------- cm

4. Focal length of the given convex lens by using (- u) versus (v) graph = ----------- cm

Precautions:

1. Tips of the object and image needles should lie at the same height as the centre of the lens.

2. Parallax should be removed from tip to tip by keeping eye at a distance at least 30 cm from the needle.

3. The object needle should be placed at such a distance that only real, inverted image of it is formed.

4. Index correction for u and v should be applied.

Sources of error:

1. The uprights may not be the vertical.

2. Parallax removal may not be perfect.

Procedure:

1. Place the optical bench in such a way that the grading on it will be visible. Otherwise rotate the optical bench.

2. Place the lens at 50 cm.3. Take half metre scale and using lens, scale and wall (face away from window / door), find the

approximate focal length of the length say f. 4. Remove the screen and place it at the end of the optical bench which is towards the basket ball

side.5. Place the needle towards the basket ball side at a distance of 2f measured from the lens and call

it object needle.6. Similarly place the second needle towards the teacher’s table at a distance of 2f from the lens

and call it as image needle. This is so because if the object is at 2f, image is also at 2f and you need to do minimum adjustments to remove parallax error.

7. Adjust the height of both the needles such that they will be approximately at the centre of the lens by using the screw placed on the needle holder.

8. Take the knitting needle and measure its actual length by using scale on the optical bench.9. Find the index error as explained under the heading of observations.10. Stand at the end of the optical bench such that your face is towards the basketball court and you

are towards the teacher’s table.11. Close your one eye and see through the lens.12. Image needle is in front of you, and through the lens will be visible the inverted image of object

needle. They might not be in the straight line. By adjusting the gap between the image needle and the inverted image of the object with the help of the screw placed at the bottom of the needle holder, make them in a straight line.

13. Hold the image needle holder in your hand. Simultaneously shift your neck shoulder to shoulder. If the image and the needle in front of you are not moving together, then there is a parallax error.

14. Under such situation, do not stop moving, and by changing the distance between the lens and the image needle by moving the image needle towards or away from the lens, you can remove the parallax so that the image and the needle starts moving together. Now it is time to take the readings. Note down the position (direct reading from the scale of the optical bench) of the image needle, lens and object needle. Your third reading is over.


15. Change the position of object needle by 2 cm towards the lens.16. To remove the parallax, go for the same procedure no 14 but shift the image needle away from

the lens. When the parallax is removed, note down the positions.17. Repeat the procedure no 16 shifting the object needle towards lens again by 2 cm. Remove

parallax and note down the reading.18. Now shift the object needle away from the lens by (2f + 2) cm. Remove the parallax by shifting

the image needle towards the lens and note down the reading.19. Repeat procedure 18 for the distance of (2f + 4) cm object distance.--------------------------------------------------------------------------------------------------------------Date: Experiment: E - Potentiometer – Comparison of EMF

Aim: To compare the emf of two given primary cells using potentiometer.Apparatus: Potentiometer, Leclanche cell, Daniel cell, two way key, one way key, galvanometer, jockey, battery, rheostatDiagram:

Theory:

E1 = k l1, E2 = k l2 (E1 / E2) = (l1 / l2)

Observations:

1. No. of wires on the potentiometer board =

2. EMF of Lechlanche cell = 1.5 V

3. EMF of Daniel cell = 1.1 V

4. Supply voltage (emf) of battery eliminator = 2.0 V


Battery

Battery

Primary cells

Battery

Galvanometer

Battery

Battery

Battery

One way key

Battery

Jockey

Battery

Battery

Battery

Observation Table:

Sr. No.

Balancing length E1 when

Lechlanche cell l1

(cm)

Balancing length E2

when Daniel cell l2

(cm)

Ratio = (E1 / E2) = (l1 / l2)

1

2

3

4

5

Mean value of the ratio of EMF’s of Lechlanche cell to Daniel cell = -------

Result: The ratio of E.M.F. of two primary cells is ----------

Precautions:


2. The plugs should be introduced in the keys only when the observations are to be taken.

3. The positive poles of the battery E and cells E1 and E2 should all be connected to the terminal at the zero of the wires.

4. The jockey should not be rubbed along the wire. It should touch the wire gently. The emf of the battery should be greater than the emf’s of the either of the two cells.

Sources of error:

1. The emf of the battery must be less than the emf’s of the either of the cells.

2. End resistances may not be zero.

3. The potentiometer wire may not be of uniform cross section and material density.

Procedure:

1. Connect the circuit as per the given circuit diagram after cleaning the ends of the wire by sand paper.

2. Insert one of the keys from two way key, touch the jockey to both the ends of the potentiometer and check for the deflection in the galvanometer in both directions. If it is not, call the teacher.


3. Adjust the value of the rheostat so that the null point or balancing length will be on the last wire. Call it l1.

4. Repeat the procedure for the next cell. Call the balancing length l2.

5. Take another four readings like this.

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Date: Experiment: E - Potentiometer – Internal resistance of a cell

Aim: To determine the internal resistance of a given primary cell (Lechlanche cell) by using a potentiometer.

Apparatus: Potentiometer, Leclanche cell, Daniel cell, resistance box, two way key, one way key, galvanometer, jockey, battery, rheostat

Theory: I = (E) / (R + r) E = I (R + r) V = I R E / V = (R + r) / (R) = 1 + (r / R) = l1 / l2

r = (E – V) (R) / (V) = (l1 – l2) (R) / (l2)

where E = emf of a battery , E1 = emf of Leclanche cell, R = resistance from the resistance box, r = internal resistance of a Leclanche cell, V = potential drop across resistance box

Diagram:

Observations:

1. No. of wires on the potentiometer board =

2. EMF of Lechlanche cell = -------- V

3. Supply voltage of battery eliminator = -------- V

4. Range of resistance box = ------- to --------


Battery

R.B

Galvanometer

JockeyOne way key

Rheostat

Primary cell

Potentiometer

Resistance box

Observation Table:

Sr. No. R (Ω)

Balancing length for Lechlanche cell in cm

r = R (l1 - l2) / l2

(Ω)Open circuit when key K2 open, only Leclanche cell is in circuit

Closed circuit when key K2

closed, Leclanche cell and resistance box are in circuit

Length l1 (cm) Length l2 (cm)

1

2

3

4

5

Result: The internal resistance of the given Lechlanche cell varies with the current drawn from it and its determined value lies between ------ Ω (minimum value) to -------- Ω. (maximum value)

Precautions:


6. The plugs should be introduced in the keys only when the observations are to be taken.

7. The positive poles of the battery E and cells E1 and E2 should all be connected to the terminal at the zero of the wires.

8. The jockey should not be rubbed along the wire. It should touch the wire gently. The emf of the battery should be greater than the emf’s of the either of the two cells.

Sources of error:

4. The emf of the battery must be less than the emf’s of the either of the cells.

5. End resistances may not be zero.

6. The potentiometer wire may not be of uniform cross section and material density.

Procedure:

6. Connect the circuit as per the given circuit diagram after cleaning the ends of the wire by sand paper.

7. Insert one of the keys from two way key, touch the jockey to both the ends of the potentiometer and check for the deflection in the galvanometer in both direction. If it is not, call the teacher.


8. Adjust the value of the rheostat so that the null point or balancing length will be on the last wire. Call it l1.

9. Repeat the procedure by inserting key for resistance box also. Call the balancing length l2.

10. Take another four readings like this.

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Date: Experiment: O – Focal Length of Concave Mirror

Aim: To find the focal length of a concave mirror by plotting graphs between - u and - v or between - 1/u and - 1/v.

Apparatus: Optical bench with three uprights: one fixed and two with lateral movement, concave mirror, mirror holder, two optical needles, a knitting needle and a half metre scale.

Diagram: Ray diagram for a concave mirror

Formula used: 1 / f = (1 / v) + (1 / u) where v is image distance and u is an object distance

Observations:

1. Approximate focal length of the given mirror = - ---------- cm

2. For index error:

Observed length of the given knitting needle = x = ---------- cm

Observed distance between the object needle and the mirror when knitting needle is placed between them = y = ------ cm

Index error for u = e1 = (y – x) = -------- cm

Index correction for u = - e1 = (x – y) ------- cm

Observed distance between the image needle and the mirror when knitting needle is placed between them = z = ------ cm

Index error for u = e2 = (z – x) = -------- cm

Index correction for u = - e2 = (x – z) ------- cm

Observation table:

Position of Object Distance - u (cm)

Image Distance - v (cm)

- 1/u cm-1

- 1/v cm-1


Sr. No.

Mirror at O (0,0)(cm)

Object needle

at A (cm)

Image needle

at C (cm)

Observed (O - A) = u' (cm)

Corrected u = u' + (-e1) (cm)

Observed (C - O) = v' (cm)

Corrected v = v' +

(-e1) (cm)

1 0

2 0

3 0

4 0

5 0

6 0

Graphs: – 1/u versus - 1/v :

- (1/u) cm-1 -(1/v)

cm-1 cm-1

Graph of: – u versus - v :

- u (cm) (0,0)

(2f,2f) - v (cm)

Calculations:

1/f = 1/v + 1/u = 1/- (-------------) + 1/- (----------------)

= - [1/(-------------) + 1/(----------------)]

= - 1 / -------- cm-1 f = - -------- cm

Result:

1. Observed focal length of the given concave mirror = - ----------- cm

2. Focal length of the given concave mirror by using formula = - ------- cm

3. Focal length of the given concave mirror by using (- 1/u) versus (- 1/v) graph = - -------- cm

4. Focal length of the given concave mirror by using (- u) versus (- v) graph = - ------- cm

Precautions:


* Origin needs to be at (0,0)* Scale along x – axis as well as y – axis must be same* Select the scale in such a way so that you can find the intercepts along x – axis as well as y – axis.Scale: 1 sq = 0.01 cm-1

** Scale along x – axis as well as y – axis must be same = 1 sq = 5 cm

* Select the scale in such a way so that you can find the intercepts if you draw a straight line at 45o from origin, it gives the coordinates of (2f, 2f)

1. Principal axis of the mirror should be horizontal and parallel to the central line of the optical bench.

2. The uprights should be vertical.

3. Top to tip parallax should be removed between the needle I and image of the needle O.

4. Tips of the object and image needle should lie at the same height as that of pole of the concave mirror.

5. Index correction for u and v should be applied.

Sources of error:

1. The uprights may not be vertical.

2. Parallax removal may not be perfect.

Procedure:

1. Place the optical bench in such a way that the grading on it will be visible. Otherwise rotate the optical bench.

2. Take half metre scale and using mirror, scale and wall (face towards the window or door), find the approximate focal length of the mirror say f.

3. Place the mirror at 0 cm (towards the basket ball court end facing towards teacher’s table).4. Place the object needle in front of the mirror at a distance of (1.5 f + 1) cm.5. Similarly place the second needle in front of the mirror at a distance more than 2f and call it as

image needle. This is so because if the object is between f and 2f, image is beyond 2f. Pierce a small piece of paper as a cap through the image needle to distinguish it from object needle.

6. Adjust the height of both the needles such that they will be at the centre of the mirror.7. Take the knitting needle and measure its actual length by using scale on the optical bench.8. Find the index error as explained under the heading of observations.9. Stand at the end of the optical bench such that your face is towards the basketball court and you

are towards the teacher’s table.10. Close your one eye and see into the mirror.11. Both the needles are in front of you, and in to the mirror will be visible the inverted images of

both needles. In all erect two needles and inverted two needles are visible.12. With the help of horizontal arrangement, place the object needle at right side while image needle

at left side or wise a versa. Adjust the mirror by rotating it such that both the inverted images are visible.

13. With the help of vertical as well as horizontal adjustment, arrange the needles in such a way that object needle will be making a straight line with the inverted image of (inverted cap needle) image needle and wise a versa.

14. Hold the image needle holder by your hand. Simultaneously shift your neck shoulder to shoulder. If the image needle (with cap) and the inverted image of object needle (without cap) in front of you are not moving simultaneously, then there is a parallax error.

15. Under such situation, do not stop moving, and by changing the distance between the mirror and the image needle (with cap), you can remove the parallax so that the image and the needle starts moving together. Now it’s time to take the readings. Note down the position (direct reading from the scale of the optical bench) of the image needle, mirror and object needle.

16. Change the position of object needle by 1 cm towards the mirror.17. To remove the parallax, go for the same procedure as 15. When the parallax is removed, note

down the positions.18. Repeat the procedure no 16 and 17 for another four readings.----------------------------------------------------------------------------------------------------------------

Date: Experiment: E Galvanometer – Resistance and Figure of merit


Aim: To determine the resistance of a galvanometer by half deflection method and to find its figure of merit and hence the current for full scale deflection.

Apparatus: A Westone type galvanometer, voltmeter, battery eliminator, two resistance boxes, two one way keys, a rheostat, screw gauge, a metre scale, connecting wires and a piece of sand paper.

Theory:

When the key K2 is kept open and K1 is closed, the current Ig through the galvanometer is given as:

Ig = Potential drop / total resistance = (E) / (R + G) Ig = k θ

Ig = (E) / (R + G) = k θ

When the key K2 is also closed and the value of resistance is so adjusted that the galvanometer needle shows a half deflection θ/2. Current Ig through the galvanometer can be determined by

1 / R’ = 1 / G + 1 / S

R’ = G S / (G + S) Total resistance = (R) + [G S / (G + S)]

Current I = (E) / {(R) + [G S / (G + S)]}

Ig’ = I {S / (G + S)} = {E / (R) + [G S / (G + S)]} {S / (G + S)

= E S / {R (G + S) + (G S)} = k (θ / 2)

Ig / Ig’ = {E / (R + G)} {[R (G + S) + G S] / (E S)} = 2R (G + S) + ( G S ) = 2 S (R + G)R G + R S + G S = 2 R S + 2 G S

R G – G S = R SG (R – S) = R S

G = (R S) / (R – S)(** For the examination purpose, you will not write this derivation. Only write formula and the meaning of the symbols used.)

Figure of merit: It is defined as the current required per division of deflection. It is denoted by letter k.

k = I / θ Ig = k θ = E / (R + G)

k = (E ) / (R + G) ( 1 / θ)


Diagram:

I. To find the resistance of the galvanometer

II. To find the figure of merit

Total number of divisions on either side of zero of the galvanometer scale = No = 30

Observation Table I: For resistance of the galvanometer

Sr. No. Resistance R (Ω)Deflection in the galvanometer θ

divisions

Half deflection

(θ /2 ) divisions

Required shunt S (Ω)

Galvanometer resistance G = (R S) / (R – S)

(Ω)

1 30 15

2 28 14

3 26 13

4 24 12

5 22 11

Mean value of galvanometer resistance = G = ------ Ω

Observation Table II: For Figure of merit and current for full scale deflection

1. Resistance of the galvanometer (G) by half deflection method = ------ Ω

2. Range of E.M.F. of the cell or battery eliminator E = 2 V to 12 V


One way key

Big resistance box

Battery

One way keySmall resistance box

One way key

Sr. No.

E.M.F. of the battery eliminator E (V)

Resistance in R.B. R (Ω)

Deflection in the galvanometer (No. of scale divisions) n

Figure of merit k=(E)/(R + G) n

1 2 30

2 4 30

3 6 30

Mean value of k = --------- ampere per division

Graph:

1/θ

(div)-1

R (Ω)

Result:

1. resistance of galvanometer by half deflection method G = ------ Ω

2. Figure of merit k = ---------- ampere per division

3. Current Ig for full scale deflection = ----------- ampere

Precautions:

1) All the connections should be neat, clean and tight.2) All the keys from the resistance boxes should be tightly pressed.3) The emf of a battery or a cell considered should be constant.4) Initially a high resistance from the resistance box should be introduced in the circuit (otherwise

for small resistance an excessive current will flow through the galvanometer and will get damaged).

Sources of error:1) The screws of the instruments might be loose providing loose connections.2) The plugs of resistance boxes may not be clean.3) The e.m.f. of a battery may not be constant.4) The divisions in a galvanometer may not be of equal size.

Procedure:a) Resistance of a galvanometer by half deflection method:

1) Make the connections of the circuit according to the circuit diagram.2) Take out around 2000 Ω resistance from the resistance box and insert key K1.


X – axis: R (Ω), Y – axis: 1/θ

Slope = m = k / E,

Intercept C = (k / E) G

By knowing k, E and C, we can find G of the galvanometer

3) Adjust the value of resistance from the box so that the deflection from the galvanometer is maximum. It should be even in number and within the scale. Note the deflection.

4) Insert key K2 also without changing any resistance from the resistance box. Adjust the value of small resistance from the small resistance box so that the deflection in the galvanometer will be exactly half of the previous one. Note down the reading.

5) Repeat the procedure from no. 2. onwards for different readings of resistance from the large resistance box.

b) Figure of merit:1) Disconnect the key K2.2) Now for different emf’s of the battery, note down the resistance taken out from the large

resistance box to achieve the maximum deflection in the galvanometer.3) Find the figure of merit by using the formula.----------------------------------------------------------------------------------------------------------------

Date: Experiment: E – Conversion of Galvanometer into Ammeter and Voltmeter

Aim: To convert the given galvanometer (of known resistance and figure of merit) into an ammeter of a desired range (0 mA to -----mA) and into a voltmeter of a desired range (0 V to -------- V) and to verify the same.

Apparatus: A Weston type galvanometer, voltmeter and ammeter of desired range, large range resistance box, small range resistance box, two one way keys, a rheostat, connecting wires and a piece of sand paper.

Diagram:

1) Conversion of Galvanometer into Ammeter of the desired range:

To convert galvanometer into ammeter: To verify the converted ammeter:

Theory: S = (Ig) G / (Io – Ig) = ρ / (Π r2): To convert it into ammeter

R = (V / Ig) – G: To convert it into voltmeter

2) Conversion of Galvanometer into Voltmeter of the desired range:

To convert galvanometer into voltmeter: To verify the converted galvanometer into voltmeter:


Observations:

1. The resistance of the given galvanometer G = --------- Ω2. Figure of merit for the given galvanometer = k = --------- ampere per division3. Total number of divisions on either side of zero = No = 304. Current for full scale deflection = Ig = No k = -----------5. Required range of the converted ammeter Io = 0 mA to --------- mA = ----------- A6. Value of shunt resistance S = (Ig) G / (Io – Ig) = ------------ Ω7. Range of the converted voltmeter = V = 0 V to ------ V8. Value of the required series resistance = R = V/Ig – G = ----------- 9. Least count of the standard voltmeter= k’’ = ------ V10. Least count of the converted ammeter k’ = I/n = ----------- A11. Least count of the standard ammeter = --------- A

Observation Table:Observation Table I: To verify the converted ammeter:

k’ = Least count of the converted galvanometer

= maximum deflection achieved in the ammeter / max no of deflection in galvanometer

Sr. No.Resistance from R. Box

(Ω)

Galvanometer reading Ammeter reading

current I’ (A)

Error = (I’ – I) (A)

No. of divisions n

Indicated current I = (k’ x n) (A)

1

2

3

4

Observation Table II: To verify the converted voltmeter:

k’’ = Least count of the converted galvanometer

= maximum deflection achieved in the voltmeter / max no of deflection in galvanometer


Sr. No.

Galvanometer reading Voltmeter reading

voltage V’ (V)

Error = (V’ – V) (V)No. of divisions n

Indicated voltage V = k’ n (V)

1

2

3

4

Result:

The resistance of the given galvanometer was found to be G = --------- Ω

Figure of merit of given galvanometer = k = ------- A div-1

Ammeter:

a) Current Ig for full scale deflection = ------------ Ab) The value of shunt required to convert the galvanometer in to the ammeter = S = ----------- Ω c) As (I’ – I) is very small, conversion is verified.

Voltmeter:

a) The value of required high resistance to be connected in series with the galvanometer to convert it into voltmeter was of the given range = --------- to --------- Ω

b) Value of the current for full scale deflection Ig = ------ Ac) As (V’ – V)) is very small, hence conversion of the given galvanometer into an voltmeter of the

given range is verified.

Precautions:

1) All the connections should be neat, clean and tight.2) The e.m.f. of the battery should be constant.3) The range of ammeter should be approximately same as the range of conversion.

Sources of error:

1) The screws of the instrument might be loose providing loose connections.2) The plugs of resistance boxes may not be clean.3) The e.m.f. of a battery may not be constant.4) The divisions in a galvanometer may not be of equal size.

Procedure:

a) Conversion of galvanometer into ammeter:

1) Count the total number of divisions in the galvanometer on either side of zero say “n”. The current for the full scale deflection Ig = n x k


2) Connect the circuit as per the diagram.3) Take out small resistance from the small resistance box.4) Adjust the rheostat so that galvanometer shows maximum deflection.5) Note down the observations.6) By changing the rheostat, note down the rest of the observations.

b) Conversion of galvanometer into voltmeter:

1) Connect the circuit according to the diagram.2) Adjust the resistance from the resistance box and the rheostat so that you should get maximum

deflection in the galvanometer.3) For rest of the observations, do not change the resistance from the rheostat.4) By changing the rheostat only, note down the rest of the observations.

----------------------------------------------------------------------------------------------------------------

Date: Experiment: O – I-V characteristics of p-n junction diode

Aim: To draw I – V characteristic curve of a p-n junction in forward bias and reverse bias.

Theory:

1. Diode conducts only in one direction.2. When positive of a diode is connected to a positive of a supply voltage and vice a versa then the

diode is said to be forward biased.3. When the diode is forward biased, the width of depletion region reduces, hence becomes easy

for charge carriers to go from one region to another.4. When negative of a diode is connected to a positive of a supply voltage and vice a versa then the

diode is said to be reversed biased.5. When the diode is reversed biased, the width of depletion region increases, hence becomes

difficult for charge carriers to go from one region to another.6. Knee voltage: The forward voltage when the current starts rising is called as knee voltage.

Below this voltage diode will not function.Diagram:

Observations:1. Maximum potential = --------- V2. Range of milliammeter = --------- mA to ------------- mA3. Least count of milliammeter = ---------- mA4. Error in the milliammeter = --------- mA5. Correction in the readings of milliammeter = ---------- mA6. Range of microammeter = --------- μA to ------------- μAAuxilary Notebook Preapared By: Dr. Pramada Lele 28 | P a g e

Voltmeter

Ammeter

Diode

Battery

One way key

Potential divider

Potential divider

0 V – 1 V range

7. Least count of microammeter = ---------- μA8. Error in the microammeter = --------- μA9. Correction in the readings of microammeter = ---------- μA10. Range of voltmeter = ---- V to -------- V11. Least count of voltmeter = -------------- V12. Error in the voltmeter = ------------- V

Observation table:** Mention whether current is measured in micro or milli ammeter.

Sr. No.

p-n junction forward biased p-n junction reversed biased

Voltmeter reading (V)

= no.of div x LC

Ammeter reading (I)

= no.of div x LC

Voltmeter reading (V)

= no.of div x LC

Ammeter reading (I)

= no.of div x LC

1

2

3

4

5

6

7

8

9

10

Graph:

Voltage along X – axis Current along Y – axis Both the graphs to be drawn on the same graph paper Draw smooth curve Calculations need to be done on the linear portion of the graph


Nature of the graph: I

V

Calculations:

Select the linear portion of the curve.

Static resistance = Rs = Vs / Is = X1 / Y1 = 1 / slope of the graph –in forward bias

= R’s = V’s / I’s = X’1 / Y’1 = 1 / slope of the graph –in reverse bias

Dynamic resistance = Rd = (X2 – X1) / (Y2 – Y1) = 1 / slope – in forward bias

R’d = (X’2 – X’1) / (Y’2 – Y’1) = 1 / slope – in reverse bias

Result:

1. The characteristic of p-n junction in forward biasing are as shown in the graph.2. The knee voltage Vk = --------- V3. Reverse break down voltage = ------------- V4. Static resistance in forward bias = ---------- Ω5. Static resistance in reversed bias = --------------- Ω6. Dynamic resistance in forward bias = ---------- Ω7. Dynamic resistance in reversed bias = --------------- Ω

Precautions:

1) All connections should be neat, clean and tight.2) Forward bias voltage applied should not be beyond the breakdown voltage.3) Reverse bias voltage applied should not be beyond the breakdown voltage.

Sources of error:

1) The junction diode supplied may be faulty.2) Connections might be wrong.3) Connectors must have broken in between.4) Meters must not be in working condition.

Procedure:

a) For forward bias:

1) Make all connections neat, clean and tight.2) Note least count of voltmeter and ammeter for two different ranges separately.3) Check for zero error.4) Gently move the potential divider from 0 V towards positive voltage and note down the readings

from ammeter and voltmeter.5) Turn the potential divider further and note down the readings. Continue for another five to six

readings keeping adequate difference between the two sets of voltage difference.6) Plot the graph and find out static, dynamic resistances and knee voltage or forward breakdown

voltage.


b) For reverse bias:

1) Make all connections neat, clean and tight.2) Change the connections for the second line of the apparatus to have reverse bias condition.3) Gently move the potential divider from 0 V towards positive voltage and note down the readings

from ammeter and voltmeter.4) Turn the potential divider further and note down the readings. Continue for another five to six

readings keeping adequate difference between the two sets of voltage difference.5) Plot the graph and find out static, dynamic resistances and reverse breakdown voltage.

----------------------------------------------------------------------------------------------------------------Date: Experiment: O - I – V characteristics of zener diode

Aim: To draw a characteristic curve of a zener diode and to determine its reverse breakdown voltage.

Theory:

1. Zener diode is always used in reverse biased condition.2. When positive of a diode is connected to a negative of a source, the diode is said to be in reverse

biased.3. In reverse biased condition, depletion layer widens and increases the barrier potential.4. As a result current decreases.5. At particular voltage, the applied electric field pulls electrons directly out of their bonds and

enhances the flow of current. This effect is called Zener effect and the potential at which it occurs is called as Breakdown voltage.

Diagram:

Observations:

1. Zener diode used : -----------2. Range of voltmeter = ---- V to -------- V3. Least count of voltmeter = -------------- V4. Error in the voltmeter = ------------- V5. Range of milliammeter = --------- mA to ------------- mA6. Least count of milliammeter = ---------- mA7. Error in the milliammeter = --------- mA8. Correction in the readings of milliammeter = ---------- mA9. Range of microammeter = --------- μA to ------------- μA10. Least count of microammeter = ---------- μA11. Error in the microammeter = --------- μA12. Correction in the readings of microammeter = ---------- μA

Observation Table:


0 V to 100 V supply

** Mention whether current is measured in micro or milli ammeter.

Sr. No.Voltmeter

Reading (V)Ammeter Reading

(A)

1

2

3

4

5

6

7

8

** Need to take the readings till for different values of current, at least for two readings, voltage remains constant.

Graph: V (V) (0,0)

Voltage along X – axis. (Scale: 1 sq = 10 V)

Current along Y – axis.

Current as well as voltage is negative.

Plot a smooth curve. I (A)

For a constant voltage extrapolate the line in dotted form and find the intercept along X – axis, which will be your breakdown voltage.

Result:

The break down voltage determined for the zener diode is ----------- V

Precautions:

1) All connections should be neat, clean and tight.2) Reverse bias voltage applied should not be beyond the breakdown voltage.

Sources of error:

1) The zener diode supplied may be faulty.2) Connections might be wrong.3) Connectors must have broken in between.4) Meters must not be in working condition.Procedure:

1) Make all connections neat, clean and tight.


2) Change the connections for the third line of the apparatus to have reversed bias condition for zener diode.

3) Select the input voltage from 0 V – 100 V.4) Gently move the potential divider from 0 V towards positive voltage and note down the readings

from ammeter and voltmeter.5) Turn the potential divider further and note down the readings. Continue the readings (till you find

constant voltage for at least three different currents) keeping adequate difference between the two sets of voltage difference.

6) Plot the graph and find out static, dynamic resistances and reverse breakdown voltage.

----------------------------------------------------------------------------------------------------------------

Date: Experiment: O - Refractive index of a glass slab

Aim: To determine the refractive index of a glass slab using a travelling microscope

Apparatus: A marker, glass slab, travelling microscope, lycopodium powder

Theory:

μ = (real depth) / (apparent depth)

real depth = R3 – R1 apparent depth = R3 – R2

Cauchy Relation: μ = A + (B/2) + (C/4) + (D/4) + ----

μ (1/) red > blue μred > μblue

Diagram: Ray diagram

Observations:

1. Least count of travelling microscope = ---------- cm

Observation Table:

Colour Readings of microscope focused on


Cross mark without slab (R1) cm

Cross mark with slab placed on it (R2) cm

Powder sprinkled on top of the slab (R3) cm

Main scale reading = M (cm)

Vernier scale division = n

Total reading = r1= M + (LC x n) (cm)



Total reading = r2 = M + (LC x n) (cm)



Total reading = r3 = M + (LC x n) (cm)

Red

Blue

Calculations:

For Red colour:

Real depth = dr = R3 – R1 = --------------- cm

Apparent depth = da = R3 – R2 = ----------- cm

Refractive index = μred = real thickness of the glass slab / apparent thickness of the glass slab

= dr / da = ------------

For Blue colour:

Real depth = dr = R3 – R1 = --------------- cm

Apparent depth = da = R3 – R2 = ----------- cm

Refractive index = μblue = real thickness of the glass slab / apparent thickness of the glass slab

= dr / da = ------------

Result: The refractive index of the glass slab by using travelling microscope for red colour is found to be ---------------and for blue colour is found to be ---------------.

Precautions:

1) Remove the parallax properly.2) Move the travelling microscope in the upward direction only to avoid the back lash error.


Sources of error:

1) The parallax must not been removed.2) The microscope scale may not be calibrated properly.

Procedure:

1) Adjust the leveling screws so that the base of the travelling microscope becomes horizontal.

2) Make microscope horizontal. Adjust the position of the eye piece so that the cross wires are clearly visible.

3) Determine the Vernier constant (least count) of the vertical scale of the microscope.

4) Mark very thin and small dot on the piece of paper with the help of blue and red ink.

5) Make the microscope vertical and focus the cross wires on it so that there is no parallax error.

6) Note down the reading. Say R1.

7) Place the glass slab on the spot made by the ink. And again focus the microscope on the spot. Remove the parallax and note down the reading. Say R2.

8) Sprinkle a few particles of the lycopodium powder on the glass slab (on the corner of the glass slab). Focus the microscope on the lycopodium powder and not on the spot. (Small fractal type shape will be visible in black colour). Remove the parallax and note down the reading. Say R3.

9) Repeat the above procedure from (5) to (8) for the other colour of the spot.

----------------------------------------------------------------------------------------------------------------

Date: Experiment: O - Refractive index of a liquid

Aim: To find refractive index of a liquid (water) using a concave mirror

Theory: μ = (real depth) / (apparent depth) = dr / da

Diagram: Ray Diagram

Observation Table:Auxilary Notebook Preapared By: Dr. Pramada Lele 35 | P a g e

Focal length of a given mirror is ------------ cm

Mean value of μ = ---------------

Result:

1. Real depth is proportional to apparent depth.

2. Refractive index of water used is ----------------.

Precautions:

1) The liquid considered should be transparent.2) Only few drops of liquid should be taken so that its layer is not thick.3) The parallax should be removed tip to tip.

Sources of error:

1) Liquid under consideration may not be transparent.2) The parallax must have not been removed.

Procedure:

1) Find the rough focal length of the concave mirror.2) Keep the concave mirror at the base of the vertical iron stand with reflecting surface facing

upwards.3) Fix an optical needle horizontally in a clamp with the stand, keeping its tip at twice the distance of

rough focal length and on vertical line through the pole of the mirror.4) Coincide the tips of the needle and its image.5) Remove the parallax properly.6) Using a plumb line and half metre scale, measure vertical distance. 7) Add water on the surface of the concave mirror.8) Repeat the procedure from (4) to (6).

----------------------------------------------------------------------------------------------------------------

Date: Experiment: O - I – V characteristics of a transistor

Aim: To study the characteristics of a common emitter n-p-n or p-n-p transistor and to find out the values of current and voltage gains.


Sr. No.Focal length of mirror in (cm)

Distance CO (cm)

Distance PO (cm)

μ = CO/PO

1

2

Theory:

For input characteristics:

1. Select a suitable value of VCE (say 4 V) by adjusting potential divider.2. Keeping VCE constant, (start by adjusting potential divider such that VBE is initially zero), vary

potential divider so as to obtain different values of VBE at intervals of 0.1 V and read the corresponding values of base current IB.

3. Repeat the above observations keeping VCE at 6 V.4. A graph of the values of IBE versus VBE would give us the input characteristics as shown in the

graph.For output characteristics:1. Adjust the potential divider such that IBE = 40 mA.2. Keeping IBE constant, vary VCE starting from 0 V at an interval of 0.05 V initially, till you reach 0.3 V

and at intervals of 2 V thereafter. Read the values of IC corresponding to the different values of VCE.

3. Adjust the values of IBE to 60 μA and repeat the earlier step. Repeat the above step by keeping IBE

= 80 μA and again at 100 μA.4. Graphs of IC versus VCE for IBE constant would give us the output characteristics as shown in the

graph.For transfer characteristics:1. Adjust potential divider so as to obtain VCE = 4 V.

2. Vary IBE in steps 10 mA (by varying potential divider) and record the corresponding values of IC till it becomes about 20 mA. Repeat these two steps for VCE = 8 V. Graph of IC versus IB is as shown in the graph.

3. Alternately to check the previous observations in earlier steps, the values of IC and IB can be read for a given value of VCE from the input and output characteristics.

Diagram:

Observations:

1. Least count of the micrometer = ---------- μA

2. Least count of milliammeter = ------------ mA

3. Least count of voltmeter VCE = ----------- V

4. Least count of voltmeter VBE = ----------- V

Observation Table:

Input characteristics (IB versus VB keeping VC constant)


n-p-n transistor Potential dividerPotential divider

AmmeterVoltmeter Voltmeter

AmmeterVoltage supply Voltage supply

I VCE = 4 V

VBE

(V)

IB

(μA)

II VCE = 6 V

VBE

(V)

IB

(μA)

*** During the readings, if the VCE is not remaining constant, then after every small change in IB, correct the reading for VCE.

Output characteristics (IC versus VCE keeping IBE constant)

IIBE = 20

μA

VCE

(V)

IC

(μA)

IIIBE = 30

μA

VCE

(V)

IC

(μA)

Transfer characteristics (IC versus IB keeping VCE constant)

IVCE = 4

V

IC

(mA)

IB

(μA)

IIVCE = 8

V

IC

(mA)

IB

(μA)


Graphs:

(a) IB versus VBE: (b) IC versus IB: (c) IC versus VCE:

IB IC IC

VBE IB IB

Calculations:

1. Input resistance = ri = QR / RS = input voltage / input current = ----------- Ω

2. Output resistance = ro = BA / AP = ∆ VC / ∆ IC = ----------- Ω

3. Current gain = β = ∆ IC / ∆ IB = ----------- at IC = ------------ mA

Result:

1. The characteristics of the given transistor ---------------- (n-p-n) is as shown in the graphs.

2. The value of the current gain β = --------

3. The value of the voltage gain AV is found to be = --------------

4. The value of input resistance = ----------

5. The value of output resistance = -----------

Precautions:

1) All connections should be neat, clean and tight.2) Forward bias voltage applied should not be beyond the breakdown voltage.3) Reverse bias voltage applied should not be beyond the breakdown voltage.

Sources of error:

1) The junction diode supplied may be faulty.2) Connections might be wrong.3) Connectors must have broken in between.4) Meters must not be in working condition.

Procedure:

1) Make all connections neat, clean and tight.2) Note least count of voltmeter and ammeter for two different ranges separately.3) Check for zero error.


a) For Input Characteristics:

1) Set the collector voltage at 6 V.2) Consider the first reading as for zero input voltage, you are getting zero current.3) Apply forward bias voltage on base junction. 4) Go on increasing the input voltage till the current starts rising suddenly. That will be your second

reading. 5) Node down the corresponding values of the current for each value of the voltage.6) Repeat procedure from (2) to (4) for the collector voltage 8 V.

b) For Ouput Characteristics:

6) Make collector voltage zero.7) Adjust the base voltage so that the input current i.e. base current 20 μA.8) In spite of collector voltage being zero, you will get collector current. Note it down.9) Consider the first reading as for zero input voltage, you are getting zero current.10)As you start increasing the output voltage, input current drops down. You need to make sure that

the input reading always remains constant.11)Repeat procedure from (6) to (10) for the base current 40 μA.

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