**Question:**

At the centre of a fixed large circular coil of radius $R$, a much smaller circular coil of radius $\mathrm{r}$ is placed. The two coils are concentric and are in the same plane. The larger coil carries a current I. The smaller coil is set to rotate with a constant angular velocity $\omega$ about an axis along their common diameter. Calculate the emf induced in the smaller coil after a time $t$ of its start of rotation.

Correct Option: 3

**Solution:**

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