Practice!

Sample Problem

The Earth's magnetic field is approximately 5.0 × 10-5 T. If an electron is travelling perpendicular to the field at 1.0 × 103 m/s, what is the radius of its path? Ignore the effects of gravity and electric field of the atmosphere. The mass of an electron is 9.1 × 10-31 kg and the charge of an electron is 1.6 × 10-19 C.

Solution

r = mv/qB

r =  (9.1 × 10-31 kg) (1000 m/s) ÷ (1.6 × 10-19 C) ÷ (5.0 × 10-5 T)  = 1.1 × 10-4 m