A square coil of side 10 cm, 500 turns and resistance 3 Ω is placed with its plane perpendicular to the horizontal component of the Earth's magnetic field. It is rotated about vertical axis passing through centre by 180° in 0.25 second. Estimate the magnitude of the emf and current induced in the coil. Horizontal component of the Earth's magnetic field at the place is 3.0 × 10^-5 T.

12 × 10^-4 V, 4 × 10^-4 A

Total area of the coil is A = Na^2 = 500\times 0.1^2 = 5m^2$

Initial Magnetic flux $ \phi_i = B.A$

Final Magnetic Flux $ \phi_f = -B.A$

Change in magnetic Flux is 2B.A

EMF is $\xi = \frac{2BA}{\Delta t} = \frac{2\times 3\times 10^{-5}\times 5}{0.25} = 12\times 10^{-4}$

Induced Current is $ I = \frac{\xi}{R} = \frac{12\times 10^{-4}}{3} = 4\times 10^{-4}A$