  ## Electromagnetic Induction

- Get to know usually which areas are frequently asked in the NEET exam
1

## Calculating induced emf due to changing area  A horizontal magnetic field B is produced across a narrow gap between the two square iron pole pieces, A closed square loop of side a. mass m and resistance R is allowed to fall with the top of the loop in the field. The loop attains a terminal velocity equal to:
Force on wire
area of

the magnetic forces on AD and BC are cancelled by each other. Magnetic field applies upward force on CD wires

which is equal to mg

A conducting loop of radius is present in a uniform magnetic field  perpendicular the plane of the ring. If radius varies as a function of time t, as  The e.m.f induced in the loop is
A
clockwise
B
clockwise
C
anticlockwise
D
zero
2

## Self inductance

Self inductance is defined as the induction of a voltage in a current-carrying wire when the current in the wire itself is changing. In the case of self-inductance, the magnetic field created by a changing current in the circuit itself induces a voltage in the same circuit. Therefore, the voltage is self-induced.The self-inductance of the coil depends on its geometry and on the permeability of the medium.
What is the self inductance of a solenoid of length cm, area of cross-section and total number of turns ?
A
mH
B
H
C
H
D
H
3

## Mutual inductance between 2 plane circular coils

Consider 2 plane circular coils close to each other having same axis. The radius of first coil is and turns and secondary coil be and turns be .
When current I flows through primary coil then magnetic field at centre be

Due to magnetic field the flux linked with secondary coil be

but
Two coils have a mutual inductance of . The current changes in the first coil according to equation , where and . The maximum value of emf (in volt) in the second coil is.
A
B
C
D
4

## Energy stored in an inductor due to a magnetic field

Example:
A long wire carries a current . Find the energy stored in the magnetic field inside a volume at a distance from the wire.
Solution:
(energy per unit volume) and

Energy

A coil carries a current of . The energy stored in joule is
A
B
C
D