Question

An electron is accelerated through a P.D of 100V and then enters a region where it is moving perpendicular
to a magnetic field B = 0.2T. The radius of the circular path is
a) 0.0167 cm
b) 0.7 cm
c) 0.2 cm
d) 0.6 cm
​

Answer 1

Answer:

The kinetic energy of electron=100e=21​mv2

⟹v=m200e​

​

The centripetal acceleration is provided by the magnetic field. Hence

rmv2​=evB

⟹mv=eBr

⟹r=eBmv​

Hence re​=0.0167cm