JEE MAIN - Physics (2020 - 3rd September Evening Slot - No. 2)

A galvanometer coil has 500 turns and each turn has an average area of 3 $$ \times $$ 10–4 m2 . If a torque of 1.5 Nm is required to keep this coil parallel to a magnetic field when a current of 0.5 A is flowing through it, the strength of the field (in T) is ______.
Answer
20

Explanation

Given N = 500

A = 3 $$ \times $$ 10–4 m2

$$\tau $$ = 1.5 Nm

i = 0.5 A

We know, $$\tau = BINA\,sin\theta $$

$$1.5 = B \times 0.5 \times 500 \times 3 \times {10^{ - 4}}$$

$$B = {{10000} \over {500}} = 20$$ Tesla

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