1
3-steps to solve problem in
physics
01
List ALL the value
given in SI units.
02
Choose a SUITABLE formula.
03
Substitute the value into the FORMULA.
Which of the following is true about the inductors?
I. They store energy over a long time
II. They resist the flow of current through it
III. They can produce a magnetic field
(A) I
(B) I and II
(C) II and III
(D) All of the above
Solution
Which of the following is true about the inductors?
I. They store energy over a long time
II. They resist the flow of current through it
III. They can produce a magnetic field
(A) I
(B) I and II
(C) II and III
(D) All of the above
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. Given :
= 2.8
L = 3 × 10−3 H
2. 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. Given :
= 400 turns
= 1.81 × 10−3 m2
= 3.4 A
l = 0.20 m
0 = 4 × 10−7 TmA−1
2. Formula :
3. Apply
Since, L = μoN2A
l
So,
= 1.05 × 10−2 J
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 36 J ,
what is the inductance of the coil?
Example for Solution
1. Given :
R = 0.3 Ω
ε = 12
= 36
2. Formula :
3. Apply
Since, =
= 12
0.3
= 40 A
So,
= 2
2
2(36)
= (40)2
= 45 × 10−3 H