(a)[3]
Define the tesla unit.
(b)
A magnet creates a uniform magnetic field of flux density $B$ in the region between its poles. A rigid copper wire carrying a current is supported on a pivot. The part $P Q L M$ of the wire lies between the poles of the magnet, as shown in Fig. 8.1. The wire is kept horizontal by a small weight $W$.
(b(i))[3]
Explain why the section $QL$ of the wire produces a moment about the pivot.
(b(ii))[2]
Explain why sections $PQ$ and $LM$ of the wire have no effect on the equilibrium of the wire.
(c(i))[2]
Show that the change in moment of $W$ about the pivot is $3.3 \times 10^{-5}\,\text{N m}$.
(c(ii))[3]
Use the information in (i) to determine the magnetic flux density $B$ between the poles of the magnet.