Phyu5june 2004 Group 2a

1.

(a)

(i)

use the voltmeter to measure the p.d. v0 across the cell. v0 = ...................................................

now set up the circuit as shown in the diagram. if you do not have an auto-ranging voltmeter, change the range of the voltmeter to 200 mv d.c. before you connect lead a to the cell, have your circuit checked by the supervisor who will allow you a short time to correct any faults. if you are unable to set up the circuit, the supervisor will set it up for you. you will lose only 2 marks for this. L ead A

+

+ 1 0 µF

V X (2)

(ii)

connect lead a to the cell in order to charge the 10 µf capacitor to the p.d. v0 of the cell. calculate the charge q stored on the 10 µf capacitor. ..................................................................................................................................... ..................................................................................................................................... use the spare lead to short circuit the capacitor x to make sure it is fully discharged. disconnect this lead, then disconnect lead a from the cell and connect it to the capacitor x. record the p.d. v across x. repeat the above procedure to find an average value for v, remembering to discharge x each time. ..................................................................................................................................... ..................................................................................................................................... (3)

(iii)

assuming that all the charge q originally stored on the 10 µf capacitor is transferred to x, calculate a value for the capacitance c of x. ..................................................................................................................................... ..................................................................................................................................... with reference to your value for c, discuss the validity of assuming that all the charge stored on the 10 µf capacitor is transferred to x. ..................................................................................................................................... ..................................................................................................................................... (3)

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(b)

(i) take suitable measurements to determine the average depth d of water in the tray. explain how you did this and record all your data below. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2)

(ii)

measure the internal width of the tray. record your value below. ..................................................................................................................................... tilt the tray by lifting one of its long sides about 1 cm above the bench. drop the side of the tray onto the bench to set up a wave, which you should be able to observe reflecting back and forth 3 or 4 times. find the time t that it takes for the wave to travel the width of the tray and hence calculate the speed υ of the wave. show all your data and calculations below. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3)

(iii)

2

theory suggests that υ = kd, where k is a constant. use your data from (i) and (ii) to calculate a value for k. ..................................................................................................................................... .....................................................................................................................................

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estimate the percentage uncertainty in your value for d and hence discuss whether k could be equal to the gravitational field strength g. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (total 16 marks)

2.

(a) determine the depression y1 of the end of the clamped metre rule when the mass hanger (i.e. a mass of 100 g) is hung from the hook at the 95 cm mark. record your readings in the table below. add to the diagram below to show how you did this. 9 5 c m m a rk

10 cm m a rk

find the depression y2 when a total mass of 200 g is hung from the hook and the depression yb when the block of wood is hung from the hook. record all your readings in the table below.

100 g 200 g block

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plot your values of y1 and y2 on the grid below. assuming a linear relationship between y and the suspended mass, determine a value for the mass m of the wooden block and its hook. m = ........................................................................................................................................ y / m m

100

m / g

200 (7)

(b)

(i) remove the block and tape a 100 g mass with its centre at the 95 cm mark of the clamped rule. determine the period t1 of small vertical oscillations of the mass. ..................................................................................................................................... ..................................................................................................................................... tape a second 100 g mass on top of the first and determine the period t2 for 200 g. ..................................................................................................................................... ..................................................................................................................................... 2

2

calculate values for t1 and t2

. 2

t1 = ............................................

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2

t2 = ........................................... 2

2

plot your values of t1 and t2 on the grid below. T 2 /s 2

100

m / g

200 (3)

(ii)

2

assuming a linear relationship between t and the suspended mass, use your graph to predict a value for the period tb when using the wooden block as the suspended mass. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3)

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(c)

2

estimate the percentage uncertainty in your value for yb in part (a) and your value for t2 in part (b). ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (3) (total 16 marks)

3.

you are to plan an investigation of how the magnetic flux density due to a current-carrying wire depends on the distance r from the wire. you are then to analyse a set of data from such an investigation. (a)

in order to plan the investigation you may assume that the following apparatus is available: • • • • • • •

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a hall probe with its power supply a meter to measure the output of the hall probe a long straight wire a 0–12 v variable d.c. power supply for the wire an ammeter to measure the current in the wire a 2.2 Ω resistor connected in series with the wire a half-metre rule

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(i)

draw a diagram of the experimental arrangement of both the wire and the hall probe. show clearly on your diagram the orientation of the sensor at the end of the probe with respect to the wire and the distance r.

(ii)

explain the purpose of the resistor in the circuit containing the wire. ..................................................................................................................................... .....................................................................................................................................

(iii)

suggest a suitable range for the ammeter that measures the current in the wire. .....................................................................................................................................

(iv)

your friend suggests that a single current-carrying wire will produce only a small magnetic flux density that is difficult to detect by means of the hall probe. suggest a modification to the apparatus that would enable a much larger flux density to be produced. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (8)

(b)

in such an investigation it is expected that

B=

µ0 I 2 πr

where b is the magnetic flux density due to the current-carrying wire, i is the current in the wire, and r is the distance from the wire at which the flux density is measured. state the graph you would plot to test the relationship between b and r. ............................................................................................................................................... ……....................................................................................................................................... the nobel school

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the following data were obtained.

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b/µt

r/m

93

0.020

74

0.025

54

0.035

38

0.050

19

0.100

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add your processed data to the third column and then plot your graph on the grid below.

(5)

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(c)

determine the gradient of your graph. hence determine a value for the current i in the wire. ............................................................................................................................................... ……....................................................................................................................................... ............................................................................................................................................... (3) (total 16 marks)

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