Question

An electron moves with a constant speed v along a circle of radius r. Its magnetic moment will be (e is the electron's charge)

• A. evr
• B. $\frac { 1 } { 2 } e v r$
• C. $\pi r ^ { 2 } e v$
• D. $2 \pi r e v$

Answer 1

Answer: (B)

$\frac { 1 } { 2 } e v r$

Answer 2

$M = i \left( \pi r ^ { 2 } \right) = \frac { e v } { 2 \pi r } \times \pi r ^ { 2 } \Rightarrow M = \frac { 1 } { 2 } e v r$