| Date | May 2013 | Marks available | 1 | Reference code | 13M.1.HL.TZ2.25 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 2 |
| Command term | Question number | 25 | Adapted from | N/A |
Question
The electric potential is VR at a point R in an electric field and at another point S the electric potential is VS. Which of the following is the work done by the electric field on a point charge +q as it moves from R to S?
A. VR-VS
B. q(VR-VS)
C. VS-VR
D. q(VS-VR)
Markscheme
B
Examiners report
This question stem needed careful reading. The discrimination index of 0.00 showed that even the better candidates were jumping to conclusions. When work is done, it must be stated clearly what it is that is doing the work, and on what. So if a weight is being lifted, then the lifter is doing (positive) work against the field, which means that the field is doing negative work on the ball. This needs to be clearly spelt out to candidates. In this case there is a charge moving in an electrical field and the candidates are being invited to state the work done by the field on the charge.
