| Date | May 2018 | Marks available | 1 | Reference code | 18M.3.SL.TZ1.3 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | State | Question number | 3 | Adapted from | N/A |
Question
The diagram shows the motion of the electrons in a metal wire carrying an electric current as seen by an observer X at rest with respect to the wire. The distance between adjacent positive charges is d.
Observer Y is at rest with respect to the electrons.
State whether the field around the wire according to observer X is electric, magnetic or a combination of both.
Discuss the change in d according to observer Y.
Deduce whether the overall field around the wire is electric, magnetic or a combination of both according to observer Y.
Markscheme
magnetic field
[1 mark]
«according to Y» the positive charges are moving «to the right»
d decreases
For MP1, movement of positive charges must be mentioned explicitly.
[2 marks]
positive charges are moving, so there is a magnetic field
the density of positive charges is higher than that of negative charges, so there is an electric field
The reason must be given for each point to be awarded.
[2 marks]
