(a)Vp/Vs = Np/Ns, rearranged to Vs = Vp × Ns/Np.

(b)For an ideal transformer, power in = power out: Vp Ip = Vs Is, so Is = Ip × Np/Ns.

(a)F = BIL.

(a)The induced e.m.f. in a circuit is proportional to the rate of change of magnetic flux linking the circuit.

(b)Move the magnet faster (increasing the rate of change of flux), or use a coil with more turns.

(a)A small current in the control circuit flows through an electromagnet (coil), which attracts an armature and closes a separate switch in the high-current circuit. This lets a low-power switch or sensor safely control a device that would otherwise draw too much current for that switch, since the two circuits are electrically separate.

(a)Vs = Vp × (Ns/Np).

(a)F = BIL.

(a)Power in = power out: Vp Ip = Vs Is, so Is = Vp Ip / Vs.

(a)Increase the current in the wire, or increase the magnetic flux density of the field (a stronger magnet).

(a)The induced e.m.f. is proportional to the number of turns, so doubling the turns doubles the induced e.m.f.

(a)As the magnet moves into the coil, the magnetic flux linking the coil changes, inducing an e.m.f. and causing a current to flow, which the ammeter detects — the faster the magnet moves, the greater the reading, since the rate of change of flux is greater.