Exam Style Answers P2 Asal Physics CB

 

 

CAMBRIDGE INTERNATIONAL AS & A LEVEL PHYSICS: COURSEBOOK 

Exam-style questions and sample answers have been written by the authors. In examinations, the way marks are awarded may be different.

 Coursebook answers Chapter P2 d

Exam-style questions 1

C 

[1]

2

D 

[1]

3

a

Dependent variable is frequency; independent variable is volume 

[1]

b

Temperature (or air pressure) 

[1]

 c

Loudspeaker connected to signal generator or tuning forks of different frequencies 

[1]

d

4

Fill with water and tip water into measuring cylinder 

[1]

f

Add water 

[1]

 g

Not too loud or use ear plugs 

[1]

a

Dependent variable is terminal velocity; independent variable is bubble volume or  radius  [1]

 c

d a b  c  

1

Temperature / mass of air in bubble / atmospheric pressure 

 f

6

[1]

a

Dependent variable is volume/radius/ diameter; independent variable is atmospheric pressure 

[1]

b

Temperature / type of balloon 

[1]

 c

Bell jar or container to hold balloon  [1] Means to change pressure, e.g., vacuum pump  [1]

d

Squirt air from a small glass tube under water wat er and change the radius of the tube [1]

e

Wrap source in a few millimetres of aluminium  and subtract background count 

[1] [1] [1]

Put a fiducial mark on the bench on the outside of the source to mark its middle Use lead absorbers / stand far aw away ay / stay close for a short time  [1]

 

Amount of radioactive material / atmospheric pressure / long half-life 

The source is quite large and it is difficult to know which part to measure to / difficult to put a ruler over the distance

g

 

[1]

[1]

[1]

Place marks on side of glass tube in which bubble bubb le rises and time bubble between the marks  [1]

Dependent variable is count rate; independent variable is distance 

Record for as long as possible (but Record much less than half-life) 

[1]  

[1]

b

5

e

Connect to a microphone and oscilloscope.. Measure T , the time for oscilloscope 1 one wave on x-axis and f  and f  = T   

 e

 

Diagram of source and GM tube, with GM tube connected to counter   [1] Record Recor d change in reading on counter and divide count by time  [1]

7

Turn on vacuum pump  Pressure gauge shown or manometer (pressure may be measured in cm of liquid) 

[1]

[1]

Wear goggles / stand behind safety screen (as bell jar may implode) 

[1]

a

6.0 ± 0.7 

[1]

b

1.5 ± 0.2 

[1]

c

9.0 ± 1.2 or 9 ± 1 

[1]

d

1.0 ± 0.3 

[1]

 e

5.0 ± 1.6 or 5 ± 2 

[1]

f

1.73 ± 0.06 

[1]

Cambridge International AS & A Level Physics – Sang, Jones, Chadha & Woodside © Cambridge University Press 2020

   

CAMBRIDGE INTERNATIONAL AS & A LEVEL PHYSICS: COURSEBOOK 

8

Best-fit line: an even balance of points about the line along its whole length  

[1]

 Worst-fit line: line with most different gradient to best-fit line but that still passes through as many error bars as possible  [1]  IIn n questions 9 to 13, only brief descriptions are given.

9

Any [4] points Any [4]  points from:

 

Use small amplitudes 

 

Trial experiment to find sensible value of mass  [1]

 

Use of electronic timer 

 

Fiducial aid 

 

Measure time from centre of oscilla oscillation tion

[1]

[1] [1]

•

Dependent variab variable le R 

 

Independent variab variable le d  

 

Constant: intensity of bulb 

[1] [1] [1]

 

Independent variab variable le I  

•

Circuit diagram 

[1]

 

Constant: coil turns and area 

 

Current and voltage measured 

[1]

•

 

Distance d between source and LDR changed 

Diagram showing coil and Hall probe with voltmeter  [1]

 

Coil connected to d.c. power supply 

 

Ammeter to measure I  

 

Probe at right angles to direction of magnetic field 

 

d measured and shown 

 

Method of measuring d   V  =    I 

[1] [1] [1]

•

R

 

Graph of ln R against ln d  should  should be a straight line (not through origin)  [1]

•

11 •

[1]

Avoid touching hot lamp / do not stare at bright light  [1]

 •

Any [4] [4] points  points from:

 

Calculation of currents and choice of sensible meter ranges 

 

Lamp is a line filament 

 

Detail of how to measure distance to filament inside bulb 

[1] [1] [1] [1]

 

Repeat measure measurement ment and average 

 

Trial experiment to find sensible distances

Dependent variab variable le B  

[1] [1] [1] [1]

[1] [1] [1] [1]

 

Method to locate centre of coil 

•

Graph Gra ph of B  against  against I or graph of ln B  

 

against ln I   [1] Straight line through origin or graph of of ln B  against  against ln I  has  has slope 1  [1]

•

Large current causes heating, so switch off when not in use  [1]

 •

Any [4] [4] points  points from:

 

Method to create a large magnetic field

[1]  

Reasoned method to keep probe in same orientation (e.g. set square, fix to rule)   [1]

[1] Avoidance of outside light/reflections  [1] Dependent variab variable le T   [1]

 

Calibrate Hall probe 

 

Repeatt experiment with probe reversed Repea

 

Independent variab variable le l  

 

   

10 •

[1] [1]

Avoid extern external al magnetic fields   Dependent variab variable le E  

[1] [1]

 

Independent variab variable le v 

[1]

 

Constant: number of turns in coil or same magnet 

[1]

Labelled diagram with magnet falling vertically through coil 

[1]

 

Constant: mass 

[1] [1]

12 •

•

Displace mass downwards and release   [1]

 

Method of measuring l  using  using rule 

 

[1] Method to measure to centre of mass  [1] Time 10 oscillations and divide by 10  [1] Use stopwatch  [1]

 

•

Graph of ln T  against  against ln l  

[1]

Voltmete oltmeterr or c.r.o. connec connected ted to coil  

 

Method to change speed of magnet 

[1] [1]

 

Gradient of graph n 

[1]

 

•

Avoid masses falling on foot / mass flying off / avoid avoid breaking ruler with large amplitudes  [1]

Measurements to find v, distance or time measurements 

[1]

   

2

•

•

 

Determining v, e.g., v = 

2h   = 2 gh or V  t

Cambridge International AS & A Level Physics – Sang, Jones, Chadha & Woodside © Cambridge University Press 2020

 

CAMBRIDGE INTERNA INTERNATIONAL TIONAL AS & A LEVEL PHYSICS: COURSEBOOK 

•

Plot graph of E  against  against v or graph of ln E   against ln v  [1]

 

Valid if straight line through origin or  gradient of log graph = +1  [1]

14 a b

i

 / T  /

 

s

[1] T 2 /

 

s2

 1.11 + 0 1.11  0..1

1.23 ± 0.02

Keep away from falling magnet / use sand tray to catch magnet  [1]

 1.28 + 0 1.28  0..1

1.64 ± 0.03

 1.42 + 0 1.42  0..1

2.02 ± 0.03

•

Any [4] Any  [4] points  points from:

 1.59 + 0 1.59  0..1

2.53 ± 0.03

 

Detailed measurement of maximum E , use of datalogger / storage oscilloscope  [1]

 1.69 + 0 1.69  0..1

2.86 ± 0.04

 

Use video including playback frame by frame  [1]

 1.81 + 0 1.81  0..1

3.28 ± 0.04

 

Use short magnet or thin coil so v is constant 

•

  [3]

 ii ii

All points plotted correctly 

[1]

[1] Cardboard tube for magnet to fall down [1] How to support coil or tube vertically  [1] Repeat for each v and average  [1] Dependent variab variable le V S  [1]

 

All error bars correct 

[1]

 iii iii

Line of best fit 

[1]

 

Worst accept acceptable able straigh straightt line 

[1]

 iv iv

4.1 s2 m 1 uncertainty between ±0.1 and ±0.3  [2]

 

Independent variab variable le f   f  

v 

 

Constant: number of turns / input current

9.6 m s 2 uncertainty between ±0.2 and ±0.6  [2]

 vi vi

Using g  = 9.6 ± 0.2 m s 2 gives t =  Using g  19.2 ± 0.2 s 

     

13 •

[1]

/ voltage to coil 

•

[1] Labelled diagram with a.c. generator   [1]

 

Voltmeter connected to output 

 

c.r.o. c.r. o. or frequency meter connected 

 

Measurement of time for one or more wave on c.r.o. screen used to find f  find f   [1]

 

Method of measuring V S; method of changing frequency 

[1]

Plot graph of V S against  against f   f  or graph of of ln V S against ln f  ln f  

[1]

•  

•

[1] [1]

Valid if straight line through origin or  gradient of log graph = +1  [1] Heating of coil, e.g. switch off when not in use to avoid overheating coil / do not touch  [1]

 •

Any [4] [4] points  points from:

 

Choice of number of turns to give reasonable reasonab le output 

 

1 f  =  period  

 

using y-gain -gain  V S found using y

 

3

4 2  g 

gradient = 

[1] [1]

[1] Changing r.m.s r.m.s.. to peak from voltmeter  [1]

 

Check that input voltage or current is constant  [1]

 

Repeat and average 

[1]

15 a

−

−

gradient n; y  y-intercept -intercept lg k  

b

c

−

 lg (T  / lg  / K)

lg (R  /  / W)

 2.436

2.740 ± 0.008

 2.452

2.681 ± 0.009

 2.467

2.625 ± 0.010

 2.481

2.568 ± 0.012

 2.496

2.519 ± 0.014

[2] [2]

[4]

i

All points plotted correctly 

[1]

 

All error bars correct 

[1]

 ii ii

Line of best fit 

[1]

 

Worst accept acceptable able straigh straightt line 

[1]

 iii iii

−

 iv iv

Use of a point on the graph and y and  y  =  mx  + c to find c about 12  mx [1]

 

Use of point on worst line graph to find value value of c about 12 ± 1   [1]

v 

3.7 ± 0.2  n = −  −3.7

[1]

 

k = 10intercept 

[1]

 

Use of worst worst value of intercept to give worst value of k   [1]

3.7 [1] ± 0.2 

[1]

Cambridge International AS & A Level Physics – Sang, Jones, Chadha & Woodside © Cambridge University Press 2020