Define magnetic flux density in terms of the force acting on a current‑carrying conductor in a magnetic field.
A particle of mass $m$ and charge $+Q$ moves at speed $v$ into a region where there is a uniform magnetic field, as shown in Fig. 7.1. State an expression, in terms of some or all of $m$, $Q$, $B$ and $v$, for the magnetic force $F$ acting on the particle at point $Y$.
On Fig. 7.1, add an arrow at point $Y$ showing the direction of the force in (b)(i).
On Fig. 7.1, draw a line that represents one possible route for the particle through the magnetic field region.
Explain how an electric field can be used together with the magnetic field so that the particle in (b) now passes through point $Z$.
Derive an expression for $v$ in terms of $B$ and the electric field strength $E$.