Physics · Oct / Nov 2022 · Paper 41 · Question 7
0625
As printed in the paper
The question as text
The electric starter motor in a car is switched on and off using a relay. The relay consists of a plastic case and two flexible springy strips, X and Y, which are made of soft iron. These iron strips act as the switch when a circuit is connected between the terminals W and Z. Fig. 7.1 shows X, Y and the plastic case. plastic case X W springy iron strips magnetising coil 12 V car battery W Z Z S X Y Y Fig. 7.1 Fig. 7.2 Fig. 7.2 shows the equipment from Fig. 7.1 inside a magnetising coil. The magnetising coil is in series with the 12 V car battery and switch S, which is open.
Read automatically from the paper; the printed page above is exact.
Show the answer and mark scheme
7(a)[3]
X and Y / they become magnetised or they / strips have poles
strips in the centre have opposite (magnetic) poles or X and Y attract
X and Y touch / close switch / activate relay / complete circuit
7(b)(i)[2]
150 A
I = P / V in any form or 1.8 / 12 or 1800 / 12 or 1800 / 12 or 0.15
7(b)(ii)[2]
small(er) resistance mentioned
less thermal energy produced or wires do not melt or large current mentioned
7(c)[2]
flexible strips in series with motor
power supply in series with motor
expected answer:
W
flexible iron
S
strips
X
12 V car
battery
Y
magnetising coil
plastic case
Z
M
starter motor
Make a free account to save your answers and see your weak topics and ask the AI why a wrong answer is wrong.