ELECTROMAGNETIC INDUCTION
10
NEF)color
one
20
movsrf)
induced
EMF
galvanometer
EMFinduced
no
fi
2.
/
--
4.
S
N
moving
out
&
-
To
induce
D
7
more
S
D
more
-
EMF induced
-
1
-
lines with the
-
>
N
of wire, there mustbe
..siff)
-
-
soil
of magnetic field
N=
stronger
magnet
7.
in
=
>
S
current
interaction
in
50
the
more
Faraday's
proportional
of turns
no
of soil of
wire
induced
EMF
->
my Electromagnetic Induction
the rate
magnetic flux linkage.
wine.
magnetic flux linkage interaction
of magnetic field with the soil
-
ENF
induced in a conductor is directly
to
more
of
change
moving the magnet faster
induced
EMF
Law
coil
a
7-
of wire
⑲
-
induced
EMF
nOEMF
induced
*
T
99
of change of
>D)
The
*
EMF
fasten the rate of change of interaction, the greater will be the
induced. *
Lenz's Law
⑲
ENFinduced
such that
which
The
=>
A
in the conductor
it
is
opposes the change
produces
it.
99
currentin the coil is such
magnetic field tries to
the motion
of magnet.
oppose
that
its
S
44474 insent: repel
D)
i.
↑(like poles G
-
1
-
conci
s
e
svor) posit
pullout:attract
MAGNETISM
AC GENERATOR
It is used to convert the rotational mechanical energy into electrical energy. It is used with
turbines that rotate and convert the rotational mechanical energy into electrical energy.
·
·
(oil Horizontal
(oil
Vertical
current
Min
currentvoltage
(zero)
Working Principle
______________________________________________________________________________
Faraday's Law of electromagnetic Induction
______________________________________________________________________________
Components
It
1. Permanent Magnets:______________________________________________________
provide a strong magnetic
field
EMF.
coil interacts
to produce
with which
________________________________________________________________________
lines
Itrotates between poles, cutting the
2. Coil: ____________________________________________________________________
field
in
EMFis
it.
induced
and
________________________________________________________________________
of
the
direction
currentin
3. Slip Rings: _______________________________________________________________
They tip
/ Voltage
max
the vertical
soil
the external
circuitwhen
crosses
________________________________________________________________________
________________________________________________________________________
position.
and
Itreduce friction
4. Carbon brushes: __________________________________________________________
provides contact
between
________________________________________________________________________
ring and external circuit.
131/199
MAGNETISM
Working Mechanism
An external source like water (hydroelectric turbines), wind (wind turbines), steam (steam
turbines in power plants) etc. are used to apply a force on the coil of wire & rotated it about the
axis b/w the magnets

When the coil winding is rotated about the fixed axis, the coil cuts the field lines of the
permanent magnet.

The cutting of the field lines by coil causes a rate of change of magnetic flux linkage.

Hence EMF (or current) is generated in the coil wire according to Faraday’s Law of
Electromagnetic Induction.
1
F1
->
↑
I/
RIGHT
Fming's
↓
HAND
A
<-
>
V
F
Thumb:Applied
force
Finger:Magnetic field
First
↳
↑
Rule
-
*
SecondFinger:Induced
current
<
S
F
1
X
·
>
vF
INITIAL POSITION
When the coil begins to rotate due to external force, current induced in the coil is carried all the
way to the external circuit. The coil is fixed to the slip rings and so is the external circuit. Hence,
as the coil rotates the slip rings rotate with it but stay in contact with the same end of the
circuit with the help of rings and carbon brushes.
133/199
MAGNETISM

After 180° of rotation of the coil, the direction of current in the ends of coil flip. As
external circuit is still attached to the same end of coil, thus the current in the external
circuit also flips its direction.
after crossing the
vertical
position
1180%)
X
F1
>
-I
T
-
L
<-
<
&
④
-F
14
↳
L
1
&
F
1
X
·
vF
AFTER 180° OF ROTATION
Describe how a
·
When
currentis
soil rotates
the
inducedin
an
AC
Generator
between the poles
cut the
permanentmagnet, they
of
these
magnetic field lines and hence
is
vale
of magnetic flux
of changeEMF
the
is induced in
a
②
a
linkage.
Hence
an
conductor.
135/199
Increase
1.
the
Increase the
magnitude of
Increase
the
induced
strength of the magnetic field
ousing stronger magnets
2.
EMF current
no.
of
ane
using radial magnets brings poles closes.
Turns
of
soil
of wire
speed/frequency of rotation.
From pulls the
4. Wind the soil
softion
hence inc. the strength
magnetic fields closer
of field)
3.
Increase
the
on
a
core.
and
MAGNETISM
Factors that increase the voltage output
1. ____________________________
Increasing the no. of
soil increases
turns
____________________________
of
N
the EMF induced as
____________________________
there is
rate
____________________________
greater
change ofmagnetic
of____________________________
flexlinkage.
2N
____________________________
turns
induced also doubles.
double,
________________________________________________________________________
If no of
voltage
________________________________________________________________________
the
2. _________________________
Increasing
strength
of
field
_________________________
magnetic
increases the EME
_________________________
I field strant
he
induced as there
_________________________
is a
late
_________________________
greater
of
_________________________
change
ofmagnetic
_________________________
thelinkage,
________________________________________________________________________
If strength doubles, EMFinducedalso double.
________________________________________________________________________
3. ___________________________
Increasing the
frequency of
rotation
___________________________
the EMF
increases
___________________________
&
1.8
#
2.8
induced.
___________________________
·
Freq.
double
double
EMF
->
->
time
half.
139/199
Transformer
Working Principle: Faraday's law of
icon
softcore
I
Induction
Electromagnetic
<
②
->
!
Vp
-
->
s
-
⑤
-
&-
Input
↓
↓
#
Explanation
Vs
An
1.
-
Secondary
voil
soil
alternating current in the
an
primacy coil creates
alternating magnetic field in
Output
Primary
·
soft ion core.
2. This
yield interacts with the
the
3.
secondary coil
and
there
of chance of
is
a
rate
magnetic flux linkage.
Hence an
the
Why were
->
They
in
secondary
transformers developed?
were
developed to
long cables.
decreasing
This
current.
decrease
was
power
achieved
EMFis
loss
induced in
coil.
during transmission
by increasing voltage and
StepDown
StepUp Transformer
input
↓
Vp
Voltage Down &
Voltage Up & CurrentDown
·
Ts
-
>
<
<
Ip
>
->
i
②
<
->
<
<
C
C
!
-S
1
i
·
Ns > Np
·
Vs > Vp
power is
as
=
I=10 x 200
ID
->
-
>
NIP Ns<Np
·
same, then
as
*
Used
↓
Vs <Vp
power is
·
vs
-
>
1 x
2008
after AC generator
before long distance transmission
<
②
-
=
Used
1
-
Is < Ip
·
*
Is
>
<
C
->
-
1Iv↑
P
Ns
NP
Vp
Up
Is
>
->
Vs
-
Current
Ip
output
↓
Transformer
same, then
Is > I p
transmission
after long distance
to decrease
voltage
back to
220/2400.
Why is
step up transforman usedbefore long distance transmission?
Step up transformes increase voltage and decrease current.
a
so
·
·
current
Less
less
causes
energy
loss
as
heat in
transmission lines.
Equations
1. N
1N0.of linens & Voltage
XV
Np
Ns
#
Vp
#P =
Vs
=
efficiency:out x100
In
Pont
efficiency:
transformer
100% efficient
Pinput Pontput
Ideal
IpVp IsVs
Ratio Method
3.
2.
-
x
Is Vs
100
Pin ->IpVp
example
Is
Ip
0.1 A
0.5 A
->
->
200V
i
1
->
->
->
->
<-
↓
500 turns
>
·i
②
C
↓
5
I
Determine
as
Voltage atsecondary coil
500 turns-200V
1500 turns-x
b)
efficiency
eff 720
=
x
100
-
x 1500 x 200
=
0.1 x 600
=
500
1500 turns
x
Vs 600V
=
=
0.5X200
eff 60%
=
x
100
Cathode
To
Ray Oscilloscope
graphically representdiv signal
a
in the
form of
Scale
Settings
1
<
x-axis.Time-base
o
e.g.
"1cm
Direct
wave.
>
·Idir
Time
a
20ms/cm
Y-axis: Y-gain
-Im
e.g.
50km
settings
20ms/dir
Voltage gain settings
5V/div
Voltage
Line
5V
D
·
5
O
Time-base:ON
50
Time-base: OFF
50
battery
battery
Alternating Voltage
~
Time-base:ON
Time-base: OFF
just one dot!
·
voltage 1.00
max
=
1.5
·
1
1.5waves
-
4ms
I wave-sh
0.5
x
=
105
O-
-
2.67mS
x
0.5
·
=
f Isof 1
=
=
2.67x10
-
1
f 375Hz
=
-
1.58
iis
↓
↑
to
is
m
-
3
The
no.
are
halved. Draw the
of turns of
coil
of the AC generator
alternating voltage
signal on the C.R.0.
new
A
Graph of
an
alternating
voltage signal.
No.
of turns
Max
Voltage
halved
halved.