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8.4 Force on
a Current-carryingconductor in
magneticField
Shahid
Mukhlis.A.G
Form 5
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Catapult Force
}When a current-carrying
conductor is placed in a magnetic
field, the interaction between the two
magnetic fields will produce aforce on the conductor, which called
a catapult force
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Fleming's Left
Hand Rule (Motor Rule)
The direction of the force can be
determined by Fleming's left
hand rule
The fore finger, middle finger and the thumb areperpendicularly to each other. The forefinger points
along the direction of the magnetic field,middle
finger points in the current direction and
the thumb points along the direction of the force.
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Strength of the Catapult Force
The strength of the force can be
increased by:
� Increase the current� Using a stronger magnet
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The Catapult Field
The interaction of the two magnetic fields (the magneticfield of the current-carrying wire and the magnetic
field of the permanent magnet) produces a resultant
field known as catapult field as shown in the figure
above.
The non-uniform field produces
the catapult force from the
stronger field to the weaker
field.
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Force between
2 current carrying conductor When 2 current carrying conductors
are placed close to each other , a
force will be generated between them.
If the current in both conductors flow in
the same direction, they will attract
each other , whereas if the currents are
in opposite direction, they will repel
each other .
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- How it's
produced and the field pattern?
This force is due to the interaction between
themagnetic field of the 2 conductor . The figureabove shows the catapult field produced by 2 current
carrying conductors when their current is in the same
direction or opposite direction.
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Turning
of a Current-carrying Coil in aMagnetic Field
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} If a current carrying coil is
placed in a magnetic field,
a pair of forces will be
produced on the coil.T
hisis due to the interaction of
the magnetic field of the
permanent magnet and
the magnetic filed of thecurrent carrying coil.
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Direct Current Motor Electric motor
converts electrical
energy to kinetic
energy. It consist
a rectangular coil
of wire placed
between 2permanent
magnets. The coil
are soldered to a
copper split ring
known ascommutator. 2
carbon brushes
are held against
the commutator.
The function of
the commutator is to change
the direction of the current in
the coil and hence change the
direction of the couple (the 2
forces in opposite direction) in
every half revolution. This is to
make sure that the coil
can rotate continuously.