950691 Physics Practicals

  • View

  • Download

Embed Size (px)

Text of 950691 Physics Practicals



LIST OF EXPERIMENTS for BE- 1 (July 2007)1. 2. 3. 4. 5. 6. 7. 8. 9. To study the characteristics of ultrasonic waves. Measurement of temperature using mercury thermometer, thermistor (PTC, NTC), thermocouple and platinum resistance (PT-100) sensors. To study p-n junction solar cell characteristics and determine its efficiency. Wavelength and energy gap determination using Newtons rings in case of Light emitting diode (LED). He-Ne laser beam parameters: laser beam power, spot size and divergence angle. To find the wavelength of light emitted by sodium vapor lamp using Fresnels biprism. To study half-wave, full-wave and bridge rectifiers. To determine the DC output voltage and the ripple factor of the bridge rectifier using a capacitor filter. To determine the resolving power of a telescope. L-I-V characteristics of a semiconductor laser (Laser Diode) and to determine its parameters.

10. To determine the value of the Rydbergs constant with the help of a spectrometer using a hydrogen gas discharge tube.



To study the properties of the ultrasonic waves. Cathode Ray Oscilloscope (CRO), Signal/Frequency generator, Ultrasonic Transducers (One Transmitter and Two Receivers), connecting wires, etc.


Interference: = d sin ; where Wavelength of the ultrasonic wave; d Separation between two transmitters; D Distance between the midpoint of the two transmitters and the receiver; x Fringe separation (i.e., x = distance between two consecutive maxima); ( x/D) Angular fringe separation.

PROCEDURE:1) 2) 3) 4)

This experiment has the following four parts:

Finding the resonance frequency of the ultrasonic transducer. Reflection of the ultrasonic waves by a flat surface. Diffraction of the ultrasonic waves through a single slit. Interference between two ultrasonic waves.

Part 1: To find the resonance frequency of the ultrasonic transducer.

Figure 1. Measurement of frequency using CRO Part A: Connect the circuit as shown in Fig. 1.

The signal generator is set for a sine wave, with the voltage range set to 30V (or, depending on the type of your signal generator, select the appropriate range for the input voltage), and the frequency range is set for 100 kHz. Adjust the appropriate knobs of the signal generator to have 6.0 Vpp and 40 kHz. Now connect the output of the function/signal generator to the channel input of the CRO. Determine the voltage and the time period (and, hence, the frequency, f = 1/T) of the signal from the function generator using the trace obtained on the CRO. NOTE: The CAL knob on the CRO should NOT be disturbed.

Part B:

Figure 2.

Determination of the resonance frequency of the transducer. (The transmitter and the receiver are represented by different symbols but they are identical in structure.)

Disconnect the signal generator from the CRO. Now connect the signal generator to the transmitter (T) as shown in Fig. 2. The receiver (R) is kept facing the transmitter about 50 cm away; the receiver is connected with the CRO at some convenient settings of volt/div and time-base knob (e.g., 0.5V/cm and 10s/cm). Resistor/potentiometer of 10k is connected as shown in the Fig. 2. To find the resonance frequency adjust the time-base knob of the CRO to obtain a sinusoidal waveform on the screen and measure its period, T, and hence calculate the frequency, f ( = 1/T). Draw the trace on the graph paper with appropriate scales.

Part 2: Reflection by a flat surface. The connections are same as that of the previous part. Now, as shown in Fig. 3, keep the receiver (R) and the transmitter (T) side by side facing a wall (or any other surface that can act as a reflector of ultrasonic waves). One should get the sinusoidal waveform. Here the variation in the amplitude can be studied by varying the position of the receiver in an arc.

Figure 3.

Reflection by a flat surface.

When both the transducers are aligned properly, i.e., i = r, one gets a maximum amplitude. Measure the period and thus find the frequency. Observe what happens for other positions of T and R.

Part 3: Diffraction through a single slit.

Figure 4. Diffraction through a single slit. To observe the diffraction of the ultrasonic waves through a slit. Here the transmitter (T) is placed about 50 cm behind the slit and the receiver (R) is placed about 25 cm in front of the slit as in Fig. 4. Observe the variation in the amplitude of the trace on the CRO by keeping the transmitter at the fixed position and moving the receiver in the transverse direction (Y-axis in Fig. 4.) The central maximum will be found near the axis of symmetry with secondary maxima and minima in the two shaded regions. Observe what happens for different distances of T and R and also for different width of the slits. Record qualitatively your observations.

Part 4: Interference property of the Ultrasonic Waves


Figure 5.

Set up to study Ultrasonic Interference.

In order to study the interference property of the ultrasonic waves we require two transmitters and one receiver as shown in Fig. 5. (Both the transmitters are connected with the signal generator whereas the receiver is connected to the CRO.) Observe the variation in the amplitude of the trace on the CRO by keeping the transmitters at the fixed positions and moving the receiver in the transverse direction (Y-axis in Fig. 5.). Note the positions for consecutive maxima. Record your observations.

OBSERVATIONS:Part 4: f = _____ Hz; D = ____ cm; d = _____ cm.

OBSERVATION TABLE:x [cm] x [cm] = (x d/D) [cm] v = f [m/s]

CALCULATIONS: {Show sample calculations for each equation used}.RESULTS: DISCUSSION OF RESULTS:


EXPERIMENT 2Aim:Measurement of temperature using mercury thermometer, thermistor (PTC, NTC), thermocouple, platinum resistance (PT-100) sensors and compare the different temperature sensors

Apparatus: Thermistor (NTC and PTC); Thermocouple (Copper Constantan); Pt 100; flask, stand,Digital Multimeter (DMM), Micro Ammeter/Voltmeter, test tube, stand, beaker, burner etc.


1-Pt 100 2-PTC 3-NTC 4-Thermocouple (Copper-constantan) 5-Test Tube 6-Beaker 7-Parafin 8-Water 9-Mercury Thermometer 10- Rubber Cork DMM Digital Multimeter DV-Digital DC micro volt ammeter K- Four point contact key K 9 1



6 2 3 4







Gas Burner4

Tripod Stand

Procedure: Connect the circuit as per given figure. Note reading at room temperature (RT). Light the gas burner and keep below the beaker kept on the tripod. Note reading at every increase (Heating) of 5 [oC] up to 75 [oC]. Repeat the same for cooling. Plot four graphs for individual sensors as shown below.


Remove the burner 1 [oC] before the required temperature (as in column-1) is reached. Wait for required temperature and note down your readings.

Observation TableTemperature [C] Room Temp. 35 40 45 50 55 60 65 70 75 NTC PTC Pt 100 Thermocouple [mV] [k] [] [] Heating Cooling Heating Cooling Heating Cooling Heating Cooling

Note: Graph:

Temperature measurement using Mercury Thermometer.

R []

R []

emf [mV]

T [oC] a) NTC/ PTC

T [oC] b) Pt 100

T [oC] c) Thermocouple


EXPERIMENT 3 AIM:To determine the current-voltage (I-V) characteristics cell for a given constant light intensity and to determine i)ii) iii) iv) v)






Open circuit voltage (Voc) Short circuit current (Isc) Fill Factor (FF) Maximum Output power (Pmax) Efficiency ()

APPARATUS: Solar Cell, Light Bulb, Digital Multimeter (DMM) and 100 ten turn potentiometer


Fill Factor (FF) =

Vmp I mp Pmax = Voc I sc Voc I sc

Efficiency () =

Pmax 1 100 A- Area of Solar Cell Pin A

Circuit Diagram:+ I -

+ Solar Cell V -

+ 100 Ohm -

PROCEDURE: A 60 watt lamp is placed above the solar cell at a distance D from it. The load resistance (100 Ohm ten turn potentiometer) is not connected into the circuit, open circuit voltage is noted. Connect the circuit as shown in the figure. The load resistance is varied with the ten turn potentiometer. Note down current value at every change of 50mV voltage. Repeat this for different intensity of light. Plot the I-V characteristics for each intensity of light and determine the efficiency.

PRECAUTIONS:Terminal = -)

The terminals of the solar cell should be connected properly (Red Terminal = + and Black

Input power (Pin) to the solar cell: Distance between lamp and solar cell D [cm] 13 10 07 Intensity of light bulb [mW/cm2] 15 25 28

(Measured using Central Electronics Limited make Suryamapi-SM201)

OBSERVATIONS:Area of the solar cell = ________cm2

OBSERVATION TABLE:For Pin = 15 [mW/cm2] V [mV] I [mA] For Pin = 25 [mW/cm2] V [mV] I [mA] For Pin = 28 [mW/cm2] V [mV] I [mA]

Note: Plot your V, I data for each input power on the same graph paper From Graph 1. I sc =______ A and I max =_______ A 2. Voc =______mV and Vmax =______mV

CALCULATIONS:1. P max = Imp x V mp 2. Fill Factor (FF) 3. Efficiency () = _______ Watt = ________ =________%

GRAPHS:V [mV] Vmax=Vmp Voc

I [mA]


Pmax = Vmax x Imax