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Magnetic Effect
A magnetic field is generated around any conductor
when an electric current flows through it.
Electric current
Wire with current
coming towards
you Wire with current
going away from
you
x
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SOLENOID
A coil generates a very concentrated (strong) magnetic field in its
center.
Electric current
x
N
S
x
x
Increasing the
number of coils
strengthens the
magnetic field.
The Right Hand Rule
can also be applied
to a solenoid!
INSIDE THE COIL THE FIELD GOES FROM SOUTH TO NORTH!!!
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Solenoid Field
• Note field same as bar magnet
• Inside S N!!!!!
Web Applet Demo>>
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Electromagnetic Induction
N S
........An electrical conductor that is accelerated
through a magnetic field will experience an
INDUCED electrical current according to
Fleming's Right Hand Rule.
Thrust
................
............
................
Forefinger
Second
Thumb
Faraday’s Law
The size of the induced current is directly proportional to the
rate of change of the magnetic flux linkage.
Current??
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Induction examples
N S
In each example the movement of the conductor is given by the red
arrow. State or show which way will the current be generated?
N S
S N
N S
1.
2.
3.
4.
N
S
S
N
5.
6.
7.
8.
S
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Electric Field Strength
• Total number of field lines is called
………………….. (…….) measured in
………………. (……)
= ……….
• = ………………….. (………)
• B = ……………………. (……)
• A = ………………. through which flux
passes
N S
+-
Magnetic field Strength (B) measured
in ……………… (………)
Thrust
1 ………….. is the field ……………. when a current of …….. A flows
through a conductor and it experiences a ………….. of …N per
meter of length.
(…
….)
(…..)
(…...)
= no of
………. in
that area.
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Electric Field Examples
• Calculate the magnetic field strength if magnetic flux of 0.5 Wb is
established over an area of 10 cm2 .
• What magnetic flux would be needed if a 1Tesla magnetic field is needed
across a 0.5m2 area?
• What area would be covered by a 100T magnetic field if the magnetic flux
density was 20 Wb?
ANSWERS >>
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Faraday’s Law
The induced emf (….) is directly proportional to the
…………. of change of …………………..
The size of the induced ……………… is (also) directly
proportional to the ………………………. of the
……………………………………...
N
t
S N
The induced emf can be increased by:
• Increasing the …………………
• Using ………………………
• Decreasing the …………. – moving
………..
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Lenz’s Law
• The induced field …….. (………………) is induced in such a way as to
……………… the ……… causing it.
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Mutual Induction
• MUTUAL INDUCTION is defined as the changing electric
…………………… producing a changing …………………….. field
which can produce a changing ………………….. in another
conductor.
• This is the basic principle of the ………………………
~
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Transformers• Ideally – all magnetic flux from primary coil links with secondary coil.
• The number of turns of wire is directly proportional to the voltage in the coil.
Np Vp
Ns Vs
— = —
How many turns of wire would you need in a
transformer that has 1000 turns in the primary and
needs to step down the voltage from 220V to 9V?
...........
Voltage
A. C
in.
.............
Voltage A. C
OUT.
STEP ................TRANSFORMER
..........
turns ..........
turns
Vp = Vs
Np Ns
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Transformers
From Faraday’s Law:
“The size of the induced current is directly proportional to the rate of change of
the magnetic flux linkage.”
• Therefore:
work done by primary = energy gained by secondary
Since W = QV and Q = It .: W = VIt
Wp = Ws
......... = ...........
........... = .............
......... = ...........
Calculate the current in the secondary coil of the 220V/9V transformer if
the current in the primary was 1.5A
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Hi -
This is a SAMPLE presentation only.
My FULL presentations, which contain a lot more more slides and other resources, are freely available
on my resource sharing website:
www.warnescience.net
(click on link or logo)
Have a look and enjoy!
WarneScience