(a)
Detailed solution: A compass needle is a small permanent magnet, so it is made of steel, which retains magnetism. The core of an electromagnet must magnetise and demagnetise easily, so soft iron is used. Transformer cores also require a material that can be rapidly magnetised and demagnetised with minimal energy loss, so soft iron is again the appropriate choice.
(b)
95 (V)
\((V_s =) 650 / 1500 \times 220\) OR 1500 / 650 = 220 / \(V_s\)
\((V_p / V_s) = (N_p / N_s)\) in any form
Detailed solution: The transformer voltage ratio equation is \(\frac{V_p}{V_s} = \frac{N_p}{N_s}\). Substituting the given values gives \(\frac{220}{V_s} = \frac{1500}{650}\). Rearranging to solve for \(V_s\) yields \(V_s = 220 \times \frac{650}{1500} = 95.3\text{ V}\), which rounds to \(95\text{ V}\) as the output voltage.
