Scribd
Upload
483 views10 pages

Self & Mutual Inductance

This document discusses the concept of self-inductance. It begins by stating the learning objectives which are to discuss self-inductance, solve problems related to self-inductance, and outline some applications. It then provides figures and equations to define self-inductance and self-induced emf. It states that self-inductance depends on the geometry of a coil and is analogous to how capacitance depends on the geometry of capacitor plates. It also discusses the time constant of self-inductance and provides examples of calculating self-inductance and self-induced emf.

Uploaded by

Imran Parvez
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
483 views10 pages

Self & Mutual Inductance

This document discusses the concept of self-inductance. It begins by stating the learning objectives which are to discuss self-inductance, solve problems related to self-inductance, and outline some applications. It then provides figures and equations to define self-inductance and self-induced emf. It states that self-inductance depends on the geometry of a coil and is analogous to how capacitance depends on the geometry of capacitor plates. It also discusses the time constant of self-inductance and provides examples of calculating self-inductance and self-induced emf.

Uploaded by

Imran Parvez
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
You are on page 1/ 10

Chapter 32

Self-Inductance
Learning Objectives
Student is expected to be able to:
• discuss self-inductance.
• solve problems related to self-inductance.
• outline some applications of self-inductance.

Figures and details shown in these slides are taken from: University Physics by Young & Freedman (11th ed),
Physics for Scientists and Engineers by Serway (5th ed), Physics for Scientists and Engineers by Giancoli (3rd ed),
and many websites.
Dr. Khalil Ebrahim, PHYCS 102, Summer
Self-Inductance

Back emf

The current I takes some finite time to reach its steady level after the switch S is
closed, likewise it takes finite time after opening S to reach zero level. This
behaviour could be explained when we define the self-inductance L which is a
results of flux change with time, but flux change resulted from filed change with
0 I
time which in turn resulted from current:
B 
 B  BA cos  2 r
Dr. Khalil Ebrahim, PHYCS 102, Summer
Self-Induced emf
Self-induced emf is always proportional to the time rate
of change of current:

dI
  L
If the current increases,
dt
the increasing magnetic
flux creates an induced
emf in the coil having the
polarity shown by the
dashed battery.
The polarity of the
induced emf reverses if
the current decreases.

Back emf
Dr. Khalil Ebrahim, PHYCS 102, Summer
Self-Inductance
The inductance of a coil depends on its geometry. This is
analogous to the capacitance of a capacitor depending on
the geometry of its plats.

Inductor vs. Capacitor NB


L
I
The SI unit of inductance
is the Henry (H)

Like capacitor an inductor


stores electric energy carried
by the magnetic field.

Dr. Khalil Ebrahim, PHYCS 102, Summer


Inductor vs. Resistor

NB
L
I

Dr. Khalil Ebrahim, PHYCS 102, Summer


Self-Inductance: Time Constant

NB
L
I

The resistance is a
measure of the
opposition to current, in
comparison, inductance
is a measure of the
opposition to a change
in current.

Dr. Khalil Ebrahim, PHYCS 102, Summer


Self-Inductance: Time Constant
Now open switch S1 and then close switch S2 a
NB
real inductance will slow the decay of the
current.
L
I

The resistance is a measure of the opposition to current, in


comparison, inductance is a measure of the opposition to a
change in current.
Dr. Khalil Ebrahim, PHYCS 102, Summer
Example
A toroidal solenoid with N = 200 turns,
A = 5.0 cm2, if r = 10 cm, determine its
self-inductance L.
Solution
 0 Ni
 B  BA  A
2 r
N  B 0 N 2
L   A
i 2 r
(4 x10 7 )(200) 2 (5.0 x10 4 )
L  40  H
2 (0.1)
Dr. Khalil Ebrahim, PHYCS 102, Summer
Example
A toroidal solenoid with N = 200 turns,
A = 5.0 cm2, and r = 10 cm, if the
current increases uniformly from zero
to 6 A in 3 s, Find the magnitude and
direction of the self-inductance emf .
Solution
dI
  L
dt
(6  0)
   (40 x10 ) 6
6
 80V
3 x10
Dr. Khalil Ebrahim, PHYCS 102, Summer
Example
If the self-inductance of a coil made of 100 turns is L = 80 mH, then the
magnetic flux through it when a current I = 10 mA passes through the
coil is:

a) 800 Wb
b) 80Wb
c) 8000 Wb
d) 12.5 Wb
e) 8 Wb

Solution
N B IL 10 2  80  10 3 6
L   B    8  10 W b
I N 100
Dr. Khalil Ebrahim, PHYCS 102, Summer

You might also like