Syllabus Edition

First teaching 2020

Last exams 2024

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Current & Potential Difference (CIE AS Physics)

Exam Questions

1 hour33 questions
1a
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3 marks

The power P dissipated in a resistor of resistance R is measured for a range of values of the potential difference V across it.

The results are shown in the table in Fig. 1.1. 

V V 2 P
1.00 1.0 0.214
1.71 2.9

0.58

2.25  

1.011

2.67  

1.43

3.00 9.0

1.80

3.27 10.7

2.176

3.50 12.3

2.43

Fig. 1.1.

For the table in Fig. 1.1

   
i)
Add the correct units.
[1]
ii)
Complete the missing data.
[1]
iii)
Identify errors in the recorded the data and correct them.
[1]

1b
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7 marks

Complete the graph of the data on Fig. 1.2. below.

    
~oWogJyv_9-1-1b-m-graph-for-current-questions
 Fig. 1.2.
   
i)
Plot the two missing points and complete the graph.
[3]
ii)
Determine the gradient of the graph.
[3]
iii)
Use the gradient of the graph to obtain a value for R.
[1]
1c
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7 marks

The rest of this question is based on the data in the table Fig. 1.1 in part (a).     

i)
Determine the value of R when V = 3.50 V.
[1]
ii)
The uncertainty in V is ± 0.01 V.
The uncertainty in P is ± 0.05 W.
Calculate the percentage uncertainty in the value of R calculated in part (i).
[3]
iii)
Hence calculate the uncertainty in the value of R.
[1]
      
iv)
State and explain whether the value of R you calculated in part (i) is consistent with the value of R you determined from the gradient in part (b).
[2]

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2a
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4 marks

The smallest conductor within a computer processing chip can be represented as a rectangular block that is one atom high, four atoms wide and twenty atoms long. One such block is shown in Fig. 1.1.

9-1-2a-m-conducting-chip

Fig. 1.1.

The block is made from phosphorus atoms of diameter d = 3.8 × 10–10 m. The atoms are deposited on an insulating surface. This ensures that the atoms touch each other.

The processing chip has a resistance, measured from P to Q, of 220 Ω.

i)
Define current.
[1]
ii)
Describe for this processing chip the properties which will affect the current.
[3]

2b
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1 mark

Calculate the number density of free electrons within the block.

Assume that each phosphorus atom contributes one free electron.

2c
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3 marks

Calculate the current between P and Q when the mean drift velocity of free electrons in the block is 1.9 × 10–5 ms–1.

2d
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3 marks

There are about 109 of these tiny conductors in a single chip each carrying the current calculated in part (c).

Estimate the total power dissipated in these conductors in a single chip.

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3a
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1 mark

A power source is connected across a component. The current in the component is 40 mA.

Calculate the total charge that flows past a point in the component in 3 minutes.

3b
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1 mark

Calculate the number of electron charge carriers passing the same point in the conductor in this time.

3c
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4 marks

8.6 J of energy are transferred to the conductor in this time.      

i)
Calculate the potential difference across the component.
[2]
ii)
Calculate the resistance of the conductor.
[2]

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