Moving Charges and Magnetism - Result Question 33
34. An electron moving in a circular orbit of radius $r$ makes $n$ rotations per second. The magnetic field produced at the centre has magnitude:
(a) Zero
(b) $\frac{\mu_0 n^{2} e}{r}$
(c) $\frac{\mu_0 n e}{2 r}$
(d) $\frac{\mu_0 n e}{2 \pi r}$
[2015]
Show Answer
Answer:
Correct Answer: 34. (c)
Solution:
- (c) Radius of circular orbit $=r$
No. of rotations per second $=n$
i.e., $T=\frac{1}{n}$
Magnetic field at its centre, $B_c=$ ?
As we know, current
$i=\frac{e}{T}=\frac{e}{(1 / n)}=e n=$ equivalent current
Magnetic field at the centre of circular orbit,
$B_c=\frac{\mu_0 i}{2 r}=\frac{\mu_0 n e}{2 r}$
