© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Electricity Foundation tier question Click anywhere on this screen to proceed. Navigate using the links at the bottom of every screen.

© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Question Explanation of question Answer Question (part 1) (a)The graph shows how the current and the potential difference are related for a long and a short wire. Complete the sentence by choosing the correct word each time. The graph with the steeper slope is the shorter / longer wire of the same material as it has a lower / higher resistance. [2] long and short wire

© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Question Explanation of question Answer Question (part 2) (b)The graph shows how the current and the potential difference are related for a thin and a thick wire. Complete the sentence by choosing the correct word each time. The graph with the steeper slope is the thin / thicker wire of the same material as it has a higher / lower resistance. [2] thin and thick wire

© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Question Explanation of question Answer Explanation of question The question addresses specification statements on current in electrical circuits. You are required to interpret the two graphs. (a) is to establish that you understand the relationship between the length of a wire and the resistance. (b) is to establish that you understand the relationship between the thickness of a wire and the resistance. In order to do this you need to remember that the longer and thinner wires have more resistance. You are not expected to explain why this is the case.

© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Question Explanation of question Answer G–E answer (a)The steeper slope is the longer wire as it has higher resistance. comment This candidate scores 3/4 which is a grade G–E standard answer. In (a), the candidate has recognised that the steeper the slope, the greater the resistance. NextPrevious.

© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Question Explanation of question Answer G–E answer (continued) (b)The graph with the steeper slope is the thinner wire of the same material as it has a lower resistance. comment In (b), the candidate has made an error by incorrectly stating that thinner wires have a steeper slope. This is a common misconception. One mark is awarded for this part. NextPrevious.

© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Question Explanation of question Answer D–C answer (a)The steeper slope is the longer wire as it has higher resistance. comment This candidate scores 4/4 which is a grade D–C standard answer. In (a), the candidate recognises that longer wires have greater resistance and that greater resistance means a steeper slope. Two marks are awarded. NextPrevious.

© Oxford University Press 2011 Unit P2 Part 2 Upgrade: Model answers 9 Question Explanation of question Answer D–C answer (continued) (b)The graph with the steeper slope is the thicker wire of the same material as it has a lower resistance. comment In (b), the candidate recognises that the steeper slope is the lower resistance, and that thicker wires have lower resistance. Two marks are awarded. NextPrevious.