Two conducting circular loops of radii R₁ and R₂ are placed in the same plane with their centres coinciding. If R₁ >> R₂, the mutual inductance M between them will be directly proportional to :

A 800 turn coil of effective area 0.05 m² is kept. perpendicular to a magnetic filed 5 × 10^–5 T. When the plane of the coil is rotated by 90^o around any of its coplanar axis in 0.1 s, the emf induced in the coil will be :

In which of the following devices, the eddy current effect is not used?

A long solenoid of diameter 0.1 m has 2 $$ \times $$ 10⁴ turns per meter. At the centre of the solenoid, a coil of 100 turns and radius 0.01 m is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to 0 A from 4 A in 0.05 s. If the resistance of the coil is 10 $$\pi $$² $$\Omega $$, the total charge flowing through the coil during this time is