The wire of a tightly wound solenoid is unwound and used to make another tightly wound solenoid of twice the diameter. The inductance changes by a factor of

The back EMF of the DC motor is ............ to speed

Eddy currents are also called

At a given instant, the current through a 60 mH inductor is 50 mA and increasing at 100 mA/ s. The energy stored at that instant is

The magnetic field within an air-cored solenoid is 0.8 T. If the solenoid is 40 cm long and 2 cm in diameter, the energy stored in its magnetic field is

A transformer has 320 turns primary coil and 120 turns secondary coil. Which of the following statements is true?

Input power at 11000 V is fed to a step-down transformer which has 4000 turns in its primary winding. In order to get output power at 220 V, the number of turns in the secondary must be

The coupling co-efficient of the perfectly coupled coils is:

The magnetic field is parallel to a surface, then the magnetic flux through the surface is :

A transformer is used to light 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A. Then the efficiency of the transformer is: