© examsnet.com
Question : 8
Total: 9
Define the term self-inductance of a solenoid. Obtain the expression for the magnetic energy stored in an inductor of self-inductance I I
Solution:
The ratio of magnetic flux through the solenoid to the current passing through it is called selfinductance of a solenoid. It is given by
L =
Energy stored in an inductor: When a current grows through an inductor, a back e.m.f. is set up which opposes the growth of current. So work needs to be done against back e.m.f. (e) in building up the current. This work done is stored as magnetic potential energy.
Let I be the current through the inductorL t
e =
The work done against induced e.m.f. ind t
d W = P dt
= − e I dt [ P = V I ]
=
I dt
= L I d I
For total work from 0 toI 0
=
L I 0 2
Hence, this work done is stored as the magnetic potential energyU
U =
L I 2
Energy stored in an inductor: When a current grows through an inductor, a back e.m.f. is set up which opposes the growth of current. So work needs to be done against back e.m.f. (e) in building up the current. This work done is stored as magnetic potential energy.
Let I be the current through the inductor
The work done against induced e.m.f. in
For total work from 0 to
Hence, this work done is stored as the magnetic potential energy
© examsnet.com
Go to Question: