A current of 10 amp. Flows through a 20 turns flat circular coil of radius 5 cm. Find the field inductions (`vecB)` at the centre of the coil.

A current of 10 Ampere flows through a coil of resistance 100 ohm. A second coil of resistance R ohm is connected across the first coil so that the current through the second coil is 8 amperes. Then the value of R in ohms is

Calculate the flux linking through a coil of single turn of area 100 cm^2 if it is laced in a magnetic field of induction 0.05 weber/m^2 so that the plane of the coil makes an angle of 30^@ to the field.