AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Current, resistance and potential difference
Current, resistance and potential difference · Electricity · Lesson 2 of 10 · 20 marks · 21 minutes
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Instructions
• Answer all the questions.
• Write your answers in the spaces provided.
• The marks for each question are shown in brackets - use this as a guide to how much to write.
• The answers are on separate pages at the back. Attempt every question before you look at them.
• Answer all questions. Use the mark allocation as a guide to how much to write.
Question 1 CALCULATE (2 marks)
The potential difference across a resistor is 9.0 V and the current through it is 0.30 A. Calculate the resistance of the resistor. Use the equation: potential difference = current × resistance
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(Total for Question 1 = 2 marks)
Question 2 CALCULATE (2 marks)
A current of 0.15 A flows through a 40 Ω resistor. Calculate the potential difference across the resistor.
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(Total for Question 2 = 2 marks)
Question 3 USE THE GRAPH (4 marks)
A student investigates how the resistance of a wire depends on its length. The graph shows the results. (a) Describe the relationship shown by the graph. (b) Use the graph to find the resistance of 70 cm of the wire. (c) Suggest why the student switched off the current between readings.
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(Total for Question 3 = 4 marks)
Question 4 DESCRIBE (6 marks)
Describe an investigation to show how the resistance of a wire depends on its length. Your answer should include a circuit diagram description, the measurements you would take, and how you would keep the test fair and safe.
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(Total for Question 4 = 6 marks)
Question 5 EXPLAIN (3 marks)
Two identical resistors are connected first in series and then in parallel. Explain, without calculation, how the total resistance of each arrangement compares with the resistance of one resistor.
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(Total for Question 5 = 3 marks)
Question 6 CALCULATE (3 marks)
A voltmeter reads 6.0 V and an ammeter reads 20 mA. Calculate the resistance of the component.
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(Total for Question 6 = 3 marks)
TOTAL FOR PAPER = 20 MARKS
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Answers and mark scheme
Check your answer only once you have written one.
Question 1 (2 marks)
R = V ÷ I = 9.0 ÷ 0.30 = 30 Ω
• Correct substitution 1 mark
• 30 Ω 1 mark
Question 2 (2 marks)
V = IR = 0.15 × 40 = 6.0 V
• Correct substitution 1 mark
• 6.0 V 1 mark
Question 3 (4 marks)
(a) The resistance is directly proportional to the length (a straight line through the origin). (b) 4.2 Ω. (c) To stop the wire heating up, because a hotter wire has a higher resistance.
• Straight line through the origin, or directly proportional 1 mark
• 4.2 Ω (accept 4.1 to 4.3) 1 mark
• To keep the temperature constant or stop the wire heating 1 mark
• Because temperature affects resistance 1 mark
Question 4 (6 marks)
See levels-of-response scheme.
• Level 3 (5 to 6 marks): a complete method with a correct circuit (ammeter in series, voltmeter across the wire), several lengths, calculation of R = V ÷ I for each, a graph, and control of temperature or safety 5 to 6 marks
• Level 2 (3 to 4 marks): a method with most of the equipment and measurements, but with gaps in the detail or control 3 to 4 marks
• Level 1 (1 to 2 marks): simple statements about measuring current and pd for wires 1 to 2 marks
Question 5 (3 marks)
In series the total resistance is greater than one resistor because the current has to pass through both. In parallel the total resistance is less than one resistor because there are two paths for the current.
• Series greater 1 mark
• Parallel less 1 mark
• A reason for either 1 mark
Question 6 (3 marks)
I = 0.020 A; R = 6.0 ÷ 0.020 = 300 Ω
• Converts 20 mA to 0.020 A 1 mark
• Correct substitution 1 mark
• 300 Ω 1 mark