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Question

Physics Question on Moving charges and magnetism

A uniform magnetic field acts right angles to the direction of motion of electrons. As a result, the electron moves in a circular path of radius 2 cm. If the speed of electrons is doubled, then the radius of the circular path will be

A

2.0 cm

B

0.5 cm

C

4.0 cm

D

1.0 cm

Answer

4.0 cm

Explanation

Solution

r=mvqBr= \frac{mv}{qB} or rvr \propto v
As v is doubled, the radius also becomes doubled.
Hence radius = 2 x 2 = 4 cm.