EXAMPLE-energy

1

An inductor of self-inductance 3 mH
is connected to a direct current
source which supplies a steady
current of 2.8 A. What is the energy
stored in the inductor?

Example for Solution

1. List information given

= 2.8
L = 3 × 10−3

2. Choose suitable formula :

3. Apply

= 1 2
2

= 1 (3 × 10−3)(2.8)2
2

= 11.76 × 10−3 J

A 400 turns solenoid has a cross
sectional area 1.81 × 10-3 m2 and

length 20 cm carrying a current of
3.4 A. Calculate the energy stored in
the solenoid

Example for Solution

1. List information given

= 400
= 1.81 × 10 − 3 2
= 3.4
l = 20
0 = 4 × 10−7 −1

2. Choose suitable formula :

3. Apply

Since, L = μoN2A
l

So,

A coil has a resistance of 0.3Ω. An
e.m.f of 12 V is applied to the coil
until equilibrium is achieved. If the
energy stored in the coil is 36J , what
is the coil’s inductance?

Example for Solution

1. List information given

R = 0.3 Ω
ε = 12
= 36

2. Choose suitable formula :

3. Apply

Since, =

= 12
0.3

= 40

So,

= 2
2

2(36)
= (40)2

= 45 × 10−3