Magnetism and Matter | Physics JEE Main questions with Solutions

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Topic Question Set

Q 1 :
A straight magnetic strip has a magnetic moment of 44 ${Am}^{2}$ . If the strip is bent in a semicircular shape, its magnetic moment will be ____ ${Am}^{2}$ (Given $π = \frac{22}{7}$ ) [2024]

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(28)

Magnetic moment of straight wire $M = 44 {Am}^{2}$

We know that, pole strength $m = \frac{M}{ℓ} \Rightarrow M = m ℓ$

If $r$ is the radius of semicircle formed by bending the strip of length $l,$ then

$π r = ℓ \Rightarrow r = \frac{ℓ}{π}$

Distance between the poles; $2 r = \frac{2 l}{π}$

Hence, new magnetic moment $(M') = m \times 2 r = \frac{M}{l} \cdot \frac{2 l}{π}$

$\Rightarrow M' = \frac{2 M}{π} = \frac{2 \times 44}{(\frac{22}{7})} = 28 {Am}^{2}$

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