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(B) The magnetic force $F$ acting on a moving charge $q$ in a magnetic field $B$ is given by the Lorentz force formula: $F = q(v 	imes B)$.Since the

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the kinetic energy of the electron remains constant

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(B) The magnetic force $F$ acting on a moving charge $q$ in a magnetic field $B$ is given by the Lorentz force formula: $F = q(v 	imes B)$.Since the magnetic force $F$ is always perpendicular to the velocity vector $v$ of the electron,the work done by the magnetic force on the electron is zero,as $W = F \cdot d = F \cdot (v \Delta t) = (F \cdot v) \Delta t = 0$.According to the work-energy theorem,the change in kinetic energy is equal to the work done by the net force. Since the work done is zero,the kinetic energy of the electron remains constant.Because the kinetic energy $(K = \frac{1}{2}mv^2)$ is constant and the mass $m$ is constant,the speed $v$ of the electron also remains constant. However,the direction of velocity changes,so momentum $(p = mv)$ is not constant,and the force direction changes as the electron moves,so the force is not constant.

An electron enters a chamber in which a uniform magnetic field is present as shown in the figure. Ignore gravity. During its motion inside the chamber:

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