Calculate the magnetic force on a moving charge and determine its direction using the right-hand rule.

What this dot point is asking

You need to calculate the magnetic force on a moving charge and determine its direction using a hand rule.

Why the charge must be moving

A stationary charge in a magnetic field feels no magnetic force. Only when the charge moves does the field push on it - and only the component of velocity perpendicular to the field contributes.

Direction: the right-hand rule

The force is perpendicular to both the velocity and the magnetic field - it cannot point along either. For a positive charge, point the fingers of your right hand along the velocity $v$, curl them toward the field $B$ (or use the flat-hand "slap" rule: fingers along $B$, thumb along $v$, palm pushes in the force direction). The force is along your thumb/palm.

Circular motion in a magnetic field

Because the magnetic force is always perpendicular to the velocity, it never changes the speed - it only changes direction. It does no work on the charge. A charge entering a uniform field perpendicular to it therefore moves in a circle, with the magnetic force providing the centripetal force (this is developed in the "charged particles in magnetic fields" dot point).

Units

The tesla is defined so that $1 \text{ T} = 1 \text{ N A}^{-1}\text{m}^{-1}$, or equivalently $1 \text{ N}$ per (coulomb-metre-per-second). A 1 T field is strong; the Earth's field is around $5\times10^{-5} \text{ T}$.