Question

A conducting wire is sliding in a uniform magnetic field. As the wire moves, emf is induced, and according to Lenz's law, motion is retarded. The work done by the magnetic field is given by $W_{magnetic}$. Then,

• A. $W_{magnetic}$ is negative, since motion is being retarded.
• B. $W_{magnetic}$ is positive since electrons are being pumped for current flow.
• C. $W_{magnetic}$ is zero, became magnetic force is always $\perp$ to velocity.
• D. None of the above.

Answer 1

The correct option is C $W_{magnetic}$ is zero, became magnetic force is always $\perp$ to velocity.

Magnetic force is always $\perp$ to velocity of a particle; hence, $Power=\overrightarrow{l}.\overrightarrow{v}=0$ or $W_{magnetic}=0$.