An Electron Moving Perpendicular to a Uniform Magnetic Field Of 0.22

Multiple Choice

An electron moving perpendicular to a uniform magnetic field of $0.22 \mathrm {~T}$ moves in a circle with a speed of $1.5 \times 10 ^ { 7 } \mathrm {~m} / \mathrm { s }$ . What is the radius of the circle? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } , m _ { \text {electron } } = 9.11 \times \right.$ 10-31 $\mathrm { kg }$ )

A) $2.2 \mathrm {~mm}$
B) $1.5 \mathrm {~mm}$
C) $0.39 \mathrm {~mm}$
D) $0.22 \mathrm {~mm}$
E) $3.9 \mathrm {~mm}$