Find the magnitude of the force on an electron that is travelling with velocity 2 x 10^4 ms^(-1) in the x direction through a uniform magnetic field of strength 2T in the y direction.
This question tells us we only need to consider the magnitude of the force, and since the magnetic field and electron's velocity are perpendicular, we can simply use the equation
F = Bqv.
We have B = 2 T, q = 1.6 x 10-19 C (the charge of an electron) and v = 2 x 104 ms-1.
Substituting these values into the equation gives
F = 2 * (1.6 x 10-19 ) * (2 x 104) = 6.4 x 10-15 N (Remember your units!)
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