(a)[2]
State the two conditions that must be met for a copper wire placed in a magnetic field to experience a magnetic force.
(b(i))[3]
On Fig. 6.1, draw arrows to show the direction of the magnetic field at each point $X$, $Y$ and $Z$.
(b(ii))[2]
Compare the magnitude of the magnetic field flux density for the pairs $X$ and $W$, and $Y$ and $Z$.
(c)[3]
Two long parallel current-carrying wires are placed close together in a vacuum. Explain why these wires exert a magnetic force on one another. You may add a labelled diagram if you wish.