Work Done by Magnetic Force on Electron · PhysicsBowl 2014 #29

Physics · electromagnetism

Problem

An electron with charge

-e

and mass

m

travels at a speed

v

in a plane perpendicular to a magnetic field of magnitude

B

. The electron follows a circular path of radius

R

. In a time

t

, the electron travels halfway around the circle. What is the amount of work done by the magnetic force on the electron in this time? (A) zero (B)

-\pi evBR

(C)

\pi evBR

(D)

-2evBR

(E)

\frac{-\pi mv}{eB}