Question

An electron does not suffer any deflections while passing through a region. This makes sure that there is no magnetic field in that region. Is the given statement true or false?

Answer 1

Since the force exerted on a charge by the field B is given by:
$\overrightarrow{F}=q(\overrightarrow{v}\times \overrightarrow{B})=qvBsin\theta$
If the motion of the electron the field is in the same direction then the net force on the charge will be zero.
So, "an electron does not suffer any deflections while passing through a region. This makes sure that there is no magnetic field in that region". This statement is not true.