Question

A chamber is maintained at a uniform magnetic field of 5 × 10^-3 T. An electron with a speed of 5 × 10^7 ms^-1 enters the chamber in a direction normal to the field. Calculate the radius of the path.

(a) 15.7 cm

(b) 5.7 cm

(c) 25.7 cm

(d) 75.7 cm

The question was asked by my college professor while I was bunking the class.

Question is taken from Motion in Combined Electric and Magnetic Field topic in chapter Moving Charges and Magnetism of Physics – Class 12

Answer 1

The correct answer is (b) 5.7 cm

The explanation is: Radius → r = \(\frac {mv}{eB}\)

r = \(\frac {(9.1 \, \times \, 10^{-31} \, \times \, 5 \, \times \, 10^7)}{(1.6 \, \times \, 10^{-19} \, \times \, 5 \, \times \, 10^{-3})}\)

r = 5.7 cm

Therefore, the radius of the path is 5.7 cm.