Summary
Electromagnetic Induction and Inductors
Lenz's Law
:
the direction of the
induced e.m.f.
, and so is the induced current if it exists, always tends to
oppose the flux change
producing it
.
Self-inductance
L in units of henry ;
Mutual inductance
Energy stored in an inductor
:
W
=
LI
2
/ 2
Different types of inductors
Transformers
Turn ratio, voltage ratio and current ratio
:
I
p
/
I
s
=
N
s
/
N
p
=
V
s
/
V
p
If
N
s
>
N
p
,
V
s
>
V
p
( a step-up transformer)
If
N
s
<
N
p
,
V
s
<
V
p
(a step-down transformer)
Autotransformers
Electromagnetic Devices
Relays
:
Loudspeakers
:
Microphones
:
Advanced Topics : Electromagnetism
(OPTIONAL)
Magnetic field and magnetic field lines
Force on a current carrying conductor
:
B
=
F / I l
and B is in tesla (T);
Fleming's left hand rule
Magnetic flux
:
= B
A
in weber (Wb)
Faraday's law of electromagnetic induction
:
the magnitude of the induced e.m.f. is proportional to the rate of change of magnetic flux linking with the conductor or the rate of flux cutting by the conductor.
Fleming's right hand rule
Magnetomotive force and magnetic field strength
Permeability
:
=
B
/
H
in henry per metre (Hm
-1
)
permeability of free space
0
= 4
10
-7
Hm
-1
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SummarySummary;history.go(0))
= B A
in weber (Wb);history.go(0))
= B / H
in henry per metre (Hm-1)0 = 4
10-7 Hm-1
Front Page
Content
Quiz