Transcript electromagnetic induction. - GTU e

Presentation is prepared by:
•Meet
Patel(13BEEEM052)
•Jaydev
Kubavat(13BEEEG049)
•Mayur
Patel(13BEEEM053)
•Parth
Gupta(13BEEEG013)
Guided By:
Prof. Krishna Chauhan
Electrical Engg. Dept.
S.V.I.T. Vasad.
Elements of Electrical Engineering(2110005)
CERTIFICATE
This to certify that
Meet Patel(13BEEEM052)
Mayur Patel(13BEEEM053)
Jaydev Kubavat (13BEEEG049)
Parth Gupta(13BEEEG016)
Of Electrical-1 has completed their Active learning Assignment
for term ending in December 2013
DATE:25/11/2013
Sign of Teacher
Head Of Department
Electromagnetic
induction
It is the process by which an emf (voltage) is
produced in a wire by a changing magnetic flux.
Magnetic flux is the product of the magnetic field
and the area through which the magnetic field
passes.
Electromagnetic induction is the principle behind
the electric generator.
The direction of the induced current due to the
induced emf is governed by Lenz’s Law.
Faraday’s law
It states that an induced emf is produced by
changing the flux, but how could the flux be
changed?
Turn the field off or on.
Move the loop of wire out of the field
Rotate the loop to change the angle between the
field and the area of the loop.
Faraday’s Law in equation form:

N
t
Where
Є = The induced emf (voltage)
(V)
ΔΦ = The change in flux (Wb)
Δt = The change in time (s)
N = number of loops.
The induced emf in the wire will
produce a current in the wire. The
magnitude of the induced current is
found using Ohm’s Law:
V  IR
  IR

I
R
Application of Faraday’s Law
 Generator
Faraday’s Law
 Show that when you integrate the emf, e with
respect to time you get the average change in
flux in time t.
d (t )
 (t )  
dt
 d
m
    (t )dt  m   m (t ) t
t2
Average value
f (t ) 
 f (t )dt
t1
t 2  t1
The Most Important Point of Faraday’s Law
A changing magnetic field produces
or creates an electric field.
Two types of electric fields. One is created by charge and the other is
created by a changing magnetic field.
Lenz’s Law
The induced current in a wire produces
a magnetic field such the flux of the
produced magnetic field opposes the
original change in flux. In simple terms
the wire resists the change in flux and
wants to go back to the way things were.
Example A current loop has an area of 40 cm2
and is placed in a 3-T B-field at the given
angles. Find the flux  through the loop in
each
case.
x x x xx
n
x x xx x
x x xA x x
x
A = 40 cm2
n
n
(a) q = 00
q
(b) q = 900
(c) q = 600
(a)  = BA cos 00 = (3 T)(0.004 m2)(1);
  12.0 mWb
(b)  = BA cos 900 = (3 T)(0.004 m2)(0);
  0 mWb
(c)  = BA cos 600 = (3 T)(0.004 m2)(0.5);   6.00 mWb
Lenz’s Law

The direction of the emf
and thus the current is
given by Lenz’s law. The
statement in bold in the
center of page 789 is a
statement of Lenz’s law.
Use this to find the
direction of the current. If
you are looking down on
the loop from above, is the
current flowing clockwise
or counter clockwise?
Explain.
Lenz’s Law
The magnetic is moving away
from the coil so the magnetic field
is decreasing, thus the current is in
a direction to off-set the decrease.
The magnetic is moving
toward the coil so the magnetic
field is increasing, thus the
current is in a direction to offset the increase.
Induced Current
When a conductor moves across flux
lines, magnetic forces on the free
electrons induce an electric current.
B
Dow
n
Right-hand force rule shows current
outward for down and inward for up
motion. (Verify)
Dow
n
F
v
I
Up
Up
B
I
v
F
B
Magnetic Flux Density
• Magnetic flux lines 
are continuous and
closed.

B
A
A
• Direction is that of the
B vector at any point.
Magnetic Flux
density:
When area A is perpendicular
to flux:

B  ;  = BA
A
The unit of flux density is the weber per square meter.

Important Terms.
alternating current - electric current that
rapidly reverses its direction
electric generator - a device that uses
electromagnetic induction to convert mechanical
energy into electrical energy
electromagnetic induction - inducing a voltage
in a conductor by changing the magnetic field
around the conductor
induced current - the current produced by
electromagnetic induction
induced emf - the voltage produced by
electromagnetic induction
Faraday’s law of induction - law which states
that a voltage can be induced in a conductor by
changing the magnetic field around the conductor
Lenz’s law - the induced emf or current in a wire
produces a magnetic flux which opposes the change
in flux that produced it by electromagnetic
induction
magnetic flux - the product of the magnetic field
and the area through which the magnetic field lines
pass.
motional emf - emf or voltage induced in a wire
due to relative motion between the wire and a
magnetic field