(a) State what is meant by a magnetic field.
(b) Fig. 8.1 shows an ammeter connected to a coil wound on a thin plastic cylinder. A small trolley is placed on a curved track which passes through the cylinder.
The trolley is released from the position shown in Fig. 8.1. It travels through the coil from right to left. The trolley travels back from left to right. It has a lower maximum speed when it travels from left to right.
The plastic cylinder does not affect any magnetic field. A magnet is fixed to the trolley.
(i) State why there is a lower maximum speed when the trolley travels back from left to right.
(ii) Fig. 8.2 shows a close-up view of the ammeter.
As the trolley enters the coil moving from right to left, the ammeter needle deflects to the left and then returns to zero.
State and explain any changes to the deflection on the ammeter as the trolley enters the coil when moving back from left to right.
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic $4.1$ — Simple phenomena of magnetism (Part $\mathrm{(a)}$)
• Topic $4.5.1$ — Electromagnetic induction (Parts $\mathrm{(b)(i)}$, $\mathrm{(b)(ii)}$)
• Topic $1.5.1$ — Effects of forces (Part $\mathrm{(b)(i)}$)
