| Date | November 2017 | Marks available | 4 | Reference code | 17N.2.HL.TZ0.8 |
| Level | Higher level | Paper | Paper 2 | Time zone | Time zone 0 |
| Command term | Compare | Question number | 8 | Adapted from | N/A |
Question
A non-uniform electric field, with field lines as shown, exists in a region where there is no gravitational field. X is a point in the electric field. The field lines and X lie in the plane of the paper.
Outline what is meant by electric field strength.
An electron is placed at X and released from rest. Draw, on the diagram, the direction of the force acting on the electron due to the field.
The electron is replaced by a proton which is also released from rest at X. Compare, without calculation, the motion of the electron with the motion of the proton after release. You may assume that no frictional forces act on the electron or the proton.
Markscheme
force per unit charge
acting on a small/test positive charge
horizontally to the left
Arrow does not need to touch X
proton moves to the right/they move in opposite directions
force on each is initially the same
proton accelerates less than electron initially «because mass is greater»
field is stronger on right than left «as lines closer»
proton acceleration increases «as it is moving into stronger field»
OR
electron acceleration decreases «as it is moving into weaker field»
Allow ECF from (b)
Accept converse argument for electron
