Define what magnetic flux density is.
A particle of mass $m$ and charge $+Q$ enters the uniform magnetic field shown in Fig. 7.1 with speed $v$. The magnetic field, which is directed into the page, has flux density $B$. The particle enters the field at point $Y$.
State an expression, using 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, draw an arrow at point $Y$ to show the direction of the force in (b)(i).
On Fig. 7.1, draw a line to show a possible path for the particle through the magnetic-field region.
Explain how an electric field can be used together with the magnetic field to ensure that the particle in (b) now passes through point $Z$.
Derive an expression for $v$ in terms of $B$ and the electric field strength $E$.