A disc of $$10.0 \mathrm{~cm}$$ diameter is rotated at speed of $$3600 \mathrm{~rpm}$$ inside a long solenoid of 1200 turns per metre on the axis of the solenoid and perpendicular to the plane of the disc. When a current of $$1.5 \mathrm{~A}$$ is passed through the solenoid, the difference in the potential between axes and circumference of the disc is nearly

The induced emf in a coil of $$10 \mathrm{H}$$ inductance in which current varies from $$9 \mathrm{~A}$$ to $$4 \mathrm{~A}$$ in $$0.2 \mathrm{~s}$$ is

A conductor of length $$5 \mathrm{~cm}$$ is moved parallel to itself with a speed of $$2 \mathrm{~m} / \mathrm{s}$$, perpendicular to a uniform magnetic field of $$10^{-3} \mathrm{~Wb} / \mathrm{m}^3$$. The induced e.m.f. generated is