Prelim p1 2010

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PARKTOWN BOYSHIGH SCHOOLDEPARTMENT OF SCIENCE

PRELIMINARY EXAMINATION

Examiner: Mr D I Mercier Moderator:Dr D Hudson-Lamb

GRADE 12LO/AS: 1/1, 1/2, 1/3, 2/1, 2/2, 2/3, 3/2

TIME: 3 h MARKS: 150 Marks

This question paper consists of 17 pagesincluding a data-sheet of 2 pages and a special answer sheet for section A

PHYSICAL SCIENCES

P1 PHYSICS30 July 2010

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Parktown Boys High School Department of Science mye/P1/Jule2010

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GENERAL INSTRUCTIONS

1. Answer ALL the questions.

2. Answer EVERY question on different FOLIO papers. Questions will be marked

separately. Write at the back of the sheet ONLY if you continue answering theSAME question.

3. Write your NAME and CLASSS on EVERY answer paper you use.

4. Non-programmable calculators may be used.

5. Appropriate mathematical instruments may be used.

6. The borrowing/lending of any material is FORBIDDEN.

7. Read the particular instructions for each section carefully (if applicable).

8. Marks may be forfeited if ALL instructions are not followed.

SECTION ASHORT QUESTIONS

INSTRUCTIONS (QUESTIONS1 AND 2)Answer ALL questions of Section A on the special ANSWER SHEET provided.

QUESTION 1: ONE WORD ANSWER

INSTRUCTIONSWrite down the word or concept that most likely represents the ideas expressed.

1.1. Device designed to transform mechanical energy into electrical energy.

1.2. Name of the electromagnetic waves used by FM radio stations in theirtransmissions.

1.3. Name of the effect that explains how our eyes transmit the informationreceived from light into electrical impulses to the brain.

1.4. Principle that explains how the particles of a medium act as a source ofnew wavelets once they are reached by a wave front.

1.5. Substances that can conduct electricity if the temperature is high enough.[5]

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QUESTION 2: MULTPLE CHOICE

INSTRUCTIONSCircle or mark with an X the correct option in the special answer sheet provided.

2.1 In the figure, the magnet is being moved away from the coil towards you with itsNorth pole in front (out of the page). Which of the following alternatives is correct?

a) Current in clockwise direction will be induced in the coil.

b) Current in anti-clockwise direction will be induced in the coil.

c) Current will appear in the magnet from North to South.

d) Current cannot be induced as theres no source of power connected.

2.2 The following graph shows the relationship between voltage and time for acertain generator:

What type of AC electrical device will be able to work with this source of power?

a) 50 Hz and 70 V

b) 25 Hz and 100 V

c) 25 Hz and 70 V

d) 50 Hz and 140 V

PLEASE TURN OVER

(V)

100 V

0,02 0,04

t(s)

-100 V

N

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2.3 The figure shows a typical diffraction pattern (for example, the one seen when alaser passes through a very narrow slit). The intensities are also shown above thelight distribution on a screen.

If the diffracted light has a wavelength of 620 nm and the slit has a width of 0,01 mm,what is the angle at which the first dark band is seen from the centre of maximumintensity (see figure).

a) 0,062

b) 3,55

c) 7,10

d) 0,0092

2.4 The magnitude of the De Broglie wavelength associated with an electron travelingat two hundred thousand meters per second is:

a) Smaller than that of visible light

b) Smaller that that of a proton traveling at the same speed

c) Similar to the wavelength of gamma rays

d) Imperceptible by any man-made machine

PLEASE TURN OVER

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2.5 A science learner has built the electrical generator shown in the figure.

What will happen as the coil is rotated?

a) The generator will work and will produce the following pattern for theemf:

b) The generator will work and will produce the following pattern for the

emf:

c) The generator will work and will produce the following pattern for theemf:

d) The generator will not work, as it only has slip rings.

PLEASE TURN OVER

(V)

t(s)

(V)

t(s)

(V)

t(s)

A

B

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2.6 Which of the following is associated with a p-n junction connected forward bias?

a) No current flows through it

b) Holes move from negative to positive

c) The depletion zone gets wider

d) p-type is connected to the positive terminal of the battery

2.7 John is performing a practical experiment to determine the speed of sound in air.Which of the following is an adequate hypothesisfor the practical?

a) What is the speed of sound in air?

b) Sound is faster in hot air than in cold air

c) 340 ms-1

d) What aspects do affect the speed of sound in air?

2.8 Which of the following equations does represent Faradays law?

a) F = q (v x B)

b) = B A cos()

c) F = I L sin()

d) = -N () / (t)

2.9 What is the wavelength of the radioactive emissions produced by the decay ofUranium in vacuum, if they have a frequency of f=1019Hz?

Uraninite, also known as Pitchblende, is the most common ore mined to extract uranium.

a) 3.33x1010m

b) 300.000 m

c) 3x10-11m

d) 3x1027mPLEASE TURN OVER

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2.10 One real life application of Infrared electromagnetic waves is:

a) Radiography

b) In remote controls

c) To cure cancer

d) To cook meals quicker

[20]

TOTAL SECTION A: [25]

SECTION BLONG QUESTIONSINSTRUCTIONS:Answer EACH ONE of the following questions in SEPARATE /

INDIVIDUAL FOLIO PAPER. Do not forget to write your name on

everyone of them.

QUESTION 3

[Start on a new folio paper]3.1 John wants to buy a new music system for his house in Miami city, Florida.

At the shop he is told that a particular brand can deliver 440 W (rms).Calculate the MAXIMUM current flowing through the system if it isconnected to a normal 110 V plug in the United States.

(3)

3.2 Plot the graph showing current versus time for the system if in the USA thefrequency of the current is 50 Hz (in reality it is 60 Hz). Show calculations

and relevant values at least for one cycle.(7)

3.3 What is going to happen to the root mean square current flowing through thesame music system if it is connected in South Africa, where the rms voltageis 220 V? Show all calculations.

(6)

3.4 In what country (USA or SA) would it seem to be safer to operate this kind of

device? Explain in one line.(2)[18]

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QUESTION 4

[Start on a new folio paper]

Consider the following set-up, in which the coil is rotated clockwise as shown:

4.1 If ABCD is a square of size 10 cm, and the magnetic field has a strength ofB=0,2 T, calculate the EMF generated in the coil when it is rotated from the

flat position as shown in the figure 45 clockwise in 0,1 s (work with alldecimal places in your calculator).

(5)

4.2 When doing what is explained in 4.1, what is the direction of the currentthrough AB? State only FROM A TO B or FROM B TO A.

(2)

4.3 What is the full name of the device to which the brushes are connected?

(2)

4.4 What is going to happen to the direction of the current in the external circuit(meaning, beyond X and Y) when the coil is rotated beyond 90? State onlyWILL BE INVERTED or WILL STAY THE SAME.

(2)

4.5 What will we need to do to convert this apparatus into an AC motor? Bespecific.

(2)[13]

X Y

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QUESTION 5


5.1 Design a practical experiment that will allow you to determine at leastapproximately the work function of a given metal which, you know, releaseselectrons when some visible lights are shone upon it.

You must include:

- Investigative question (1)

- List of apparatus (4)

- Procedure / Method (5)

- State one controlledvariable, independentvariable and one dependantvariable for this practical. (3)

5.2 Let us assume that after perfoming your practical experiment, you find out thatthe metal has a work function of W = 9x10

-19J.

What will the speed of the electrons emmitted from the metallic plate be, if lightof wavelength = 150 nm is radiated on it?

(5)

[18]

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QUESTION 6


An ambulance approaches an injured person at a constant speed. The person lies onthe floor. The siren of the ambulance emits a sound of frequency of 600 Hz. Assumethe speed of sound in air is 340 ms-1.

6.1 After the ambulance had passed a policeman (see figure), he reckons the ambulancemoves at 10 ms-1. What frequency will the policeman hear?

(4)

6.2 What frequency will the person lying on the floor hear?(4)

6.3 The ambulance had to stop due to traffic, and another person who has beenlooking after the person lying on the floor runs towards the ambulance. Heperceives the frequency of the siren at 610 Hz. Calculate the speed of this runningperson.

(4)

6.4 A blind man stands next to the road while the ambulance is still moving. Explain whatproperty/effect/principle will help the blind man to know if the ambulance is movingtoward him or away from him.

(2)

[14]

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QUESTION 7


Consider the following RC circuit, in which the battery has an emf of 12 V andnegligible internal resistance, and the resistance R = 2 .

7.1 If the parallel plates capacitor has the following characteristics:

Distance between the plates: 0.01 mmArea of the plates: 1 mm2

Calculate the capacitance of the capacitor, if no dialectric material is being used. (4)

7.2 Calculate the charge stored in the capacitor when it is fully charged. (3)

7.3 Calculate the voltage across the resistance when the capacitor is 75% charged. (5)

If initially the switch is moved to position A;

7.4 Sketch a simple graph current (in amperes) versus time (in seconds) to show how

the reading in the ammeter will change (no numbers needed). (5)

Once the capacitor is fully charged, the switch is moved to position B;

7.5 Sketch a simple graph current (in amperes) versus time (in seconds) to show howthe reading in the ammeter will change (no numbers needed). (5)

7.6 Mention one real life application in which a capacitor is used. Be specific (forexample the answer a fridge is not good enough). (2)

[24]

A

B

A

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QUESTION 8


8.1 Sketch a full labeled diagram showing the set-up for the experiment performed byThomas Young to analyze the interference pattern of light. Mention all relevantaspects. (5)

8.2 Sketch a figure showing how this pattern will look. (2)

8.3 Mention 2 differences between the pattern in 8.2 and the pattern due to purediffraction of light. (2)

8.4 The figure shows 2 points producing two waves in phase on water. The wavelengthis = 4 cm.

If point P is located on themedium so that:

AP = 16 cm

And

BP = 34 cm

What kind of interference will we see at P? (State only CONSTRUCTIVE orDESTRUCTIVE) (2)

8.5 Briefly explain your answer in 8.4 (show calculations!) (4)[15]

A

P

B

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QUESTION 9


In the circuit represented below, the battery has an emf of 10 V and an unknowninternal resistance. Voltmeter V1is connected across the battery and voltmeter V2isconnected across the open switch S. The resistance of the connecting wires andammeter can be ignored.

If Switch S is open.

9.1 What is the reading on V1? (1)


When switch S is closed, the reading on V1drops to 7,5 V.


9.4 Calculate the reading on the ammeter. (4)

9.5 Calculate the internal resistance of the battery. (4)

[13]

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QUESTION 10


A small conducting sphere X with a charge of +5x10-9C is suspended by an inelasticthread of negligible mass which is tied to point P. Another small, conducting sphereY, on an insulated stand, with a charge of 8x10-9C is moved towards X until theircentres are 20 mm apart.

10.1 Calculate the magnitude and direction of the electrostatic force thatsphere Y exerts on sphere X. (4)

Sphere Y is now moved closer and forced to make make contact with sphere X.

Then sphere X is repelled and comes to rest with the centres of the spheres 10 mmapart. Sphere Y remains at a point directly below P such that the spheres X and Yare on the same horizontal level (see diagram below).

10.2 Calculate the new charge on sphere X after they have touched each other. (2)

10.3 Calculate the new magnitude and direction of the electrostatic force thatsphere Y exerts on sphere X. (4)

[10]

TOTAL SECTION B: [125]

TIME: 3 h GRAND TOTAL: 150 Marks

P

20 mm

X Y

+5x10-9

C -8x10-9

C

P

10 mm

X Y

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DATA FOR PHYSICAL SCIENCES P1GRADE 12

TABLE 1: PHYSICAL CONSTANTSNAME SYMBOL VALUE

Acceleration due to gravity g 9,8 ms-2

Speed of light in a vacuum c 3,0 x 108ms-1

Planck's constant h 6,63 x 10-34Js

Gravitational constant G 6,67 x 10-11Nm2kg-2

Coulomb's constant k 9,0 x 109 Nm2C-2

Charge on electron e- -1,6 x 10-19C

Electron mass me 9,11 x 10-31kg

Permittivity of free space 0 8,85 x 10-12Fm-1

Permeability of free space 0 4 x 10-7TmA-1

TABLE 2: FORMUL

MOTION

tavv if += 2

21

i tatvx += or2

21

i tatvy +=

xa2vv2i

2f += or ya2vv

2i

2f += t2

vvx if

+= or t

2

vvy if

+=

FORCE

maFnet = mvp=

if mvmvptF == mgFg =

WORK, ENERGY AND POWER

xFW = cos() U = mghEP=

2k mv

2

1EK == kikfk EEEKW ===

t

WP

= FvP=

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WAVES, LIGHT AND SOUND

= fv or v ==== f

1T = or

=

1T

s

s

LL f

vvvvf

= hfE= or =hE or

= chE

vm

h= sin

a

m=

2

0 mv2

1Whf +=

2

1

sin

sin

v

v=

MATTER AND MATERIALS

xkF = StressAF=

2)(

2

1xkW = Strain

l

x=

ELECTRICITY AND MAGNETISM

2

II maxRMS = and

2

VV maxRMS =

t

N

=

= BAcos()

RMSRMSaverage IVP =

R

VP

2RMS

average =

ELECTROSTATICS

2

21

r

QkQF=

2r

kQE=

d

VE=

r

QkQU 21=

QFE= ItQ=

C =V

Q C =

d

A0

ELECTRIC CIRCUITS

I

VR= ...

R

1

R

1

R

1

21p

++=

...RRR 21s ++= )rR(IEmf +=

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SPECIAL ANSWER SHEET FOR SECTION A

DETACH THIS PAGE AND PUT IT AT THE FRONT OF YOU ANSWER PAPER

NAME: DATE: CLASS:

QUESTION 1: ONE WORD ANSWER .

1.1

1.2

1.3

1.4

1.5[5]

QUESTION 2: MULTIPLE CHOICE .

[2X10=20]

2.1 A B C D

2.2 A B C D

2.3 A B C D

2.4 A B C D

2.5 A B C D

2.6 A B C D

2.7 A B C D

2.8 A B C D

2.9 A B C D

2.10 A B C D

SEC A Q3 Q4 Q5 Q6 Q7 Q8 Q19 Q10 TOTAL

25 18 13 18 14 24 15 13 10 150

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Prelim p1 2010