Pick out the wrong statement.

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(D) The magnetic force on a moving charge is given by $F = q(v 	imes B)$. If the electron is at rest $(v = 0)$,the force is zero. Thus,option $A$ is

Vedclass · Accepted Answer

An electron moving in the direction of the electric field gains $KE$.

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(D) The magnetic force on a moving charge is given by $F = q(v 	imes B)$. If the electron is at rest $(v = 0)$,the force is zero. Thus,option $A$ is correct.When an electron moves at right angles to a magnetic field,the force is always perpendicular to the velocity,so no work is done and the kinetic energy remains constant. Thus,option $B$ is correct.When an electron enters an electric field at right angles,it experiences a constant force perpendicular to its initial velocity,resulting in a parabolic trajectory. Thus,option $C$ is correct.An electron is negatively charged,so it experiences an electrostatic force $F = -eE$ opposite to the direction of the electric field. If it moves in the direction of the electric field,it is decelerated,meaning it loses kinetic energy. Thus,option $D$ is the wrong statement.

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