A uniform magnetic field acts at right angles to the direction of motion of electron. As a result, the electron moves in a circular path of radius 2cm. If the speed of electron is doubled, then the radius of the circular path will be.
2.0 cm
0.5 cm
4.0 cm
1.0 cm
As v is doubled, the radius also becomes double. Hence, radius = 2 x 2 = 4 cm