EMI 3

Question 1

what is the energy stored in an inductor

Answer 1

as the current starts to increase through the coil, the induced emf developed opposes the growth of current.

SO source emf has to spend energy to send current against the induced/back emf and this w done is stores as energy in the inductor

Question 2

comparision of electrostatic energy with magnetic energy

Answer 2

electrostatic energy stored in a capacitor is given by
Ue= 1/2E^2 epsilon not

Magnetic energy stores in inductor is given by
Um=B^2/2uo

Question 3

what happens when 2 current carrying coils are placed together

Answer 3

Consider the general case of currents flowing simultaneously in two
nearby coils. The flux linked with one coil will be the sum of two fluxes
which exist independently.

E=-Ldi/dt- Mdi/dt

Question 4

what is an ac generator/ ac dynamo

Answer 4

it is a device that converts mechanical energy into electrical energy ( alternating current)

Question 5

principle of ac gen

Answer 5

it is based ont he principle of electromagnetic induction

an emf is induced in the coil, wheneer there is a change in magnetic flux linked the coil

Question 6

construction

Answer 6

i) Armature- it is rectangular coil whcih contains a large no of turns of insulated coopper wire wound over a soft iron core. It is rotated about central axis.

ii) Field magnet- it is concave shapes cylindrical pieces of magnet that are used to produce a radial field.(aa radial magnetic field ensures that the magnetic flux linking with the coil changes uniformly as the rotor spins.)

iii) slip rings - They are 2 metallic rings to which the arms of the coil is connected. They rotatate along with the coil.

iv) Brushes- theyare 2 flexible carbon brushes. They are kept in light contact with the rings.

Question 7

uses of slip rings

Answer 7

In an AC dynamo (alternator), slip rings are used to maintain a continuous electrical connection between the rotating coil (rotor) and the external circuit while allowing the rotor to spin freely.

Question 8

use of carbon brushes

Answer 8

purpose of brushes is to pass the induced current from the armature coil to the external load resistance

Question 9

working of a coil

Answer 9

As the the coil is rotated, the angle theta between the magnetic field and the normal to the plane of the armature coil changes continuously

hence the magnetif flux linked with the armature coil changes continuously

this results in the generation of an induced emf and current in the coil.