Question 192: Magnetism and Matter

Question

A thin ring of 10 cm radius carries a uniformly distributed charge. The ring rotates at a constant angular
speed of 40 $$\pi $$ rad s–1
 about its axis, perpendicular to its plane. If the magnetic field at its centre is 3.8 × 10–9
T, then the charge carried by the ring is close to ($$\mu $$0 = 4$$\pi $$ × 10–7
 N/A2
).

Accepted Answer

$$B = {{{\mu _0}i} \over {2a}}{{\omega q} \over {2\pi }} = i$$
$$B = {{{\mu _0}} \over {2a}}.{{\omega q} \over {2\pi }}$$
$$B = {{{{10}^{ - 7}} 	imes 40} \over {0.1}} 	imes q 	imes \pi $$
$$ \Rightarrow q = 3 	imes {10^{ - 5}}C$$

Answer

7 × 10–6 C

Answer

4 × 10–5 C

Answer

2 × 10–6 C

Answer

3 × 10–5 C

Magnetism and Matter

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