(a(i))[3]
When a direct current is switched on in the wire, the balance reading decreases. State and explain the direction of the force on the wire.
(a(ii))[2]
When a direct current is switched on in the wire, the balance reading decreases. State and explain the direction of the current in the wire.
(b)[3]
A direct current of $4.6\,\text{A}$ in the wire changes the balance reading by $4.5 \times 10^{-3}\,\text{N}$. This direct current is then replaced by an alternating current of frequency $40\,\text{Hz}$ and root-mean-square (r.m.s.) value $4.6\,\text{A}$. On the axes of Fig. 8.2, sketch a graph to show how the balance reading changes over a time of $50\,\text{ms}$.