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Published by haz imah, 2019-11-01 19:35:49

PROBLEM-SOLVING (Energy)

EXAMPLES

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


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