Unit 5 Day 2: Induced EMF in a Moving Conductor Induced EMF in a Moving Conductor in a Magnetic...
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Transcript of Unit 5 Day 2: Induced EMF in a Moving Conductor Induced EMF in a Moving Conductor in a Magnetic...
Unit 5 Day 2: Induced EMF in a Moving Conductor
• Induced EMF in a Moving Conductor
in a Magnetic Field
• Force Required to Move a Moving
Conductor in a Uniform Magnetic
Field
• Electric Generators (AC)
Induced EMF in a Moving Conductor in a Magnetic Field
• The B-Field is out of the paper and perpendicular to a U-shaped conductor with a movable rod, moving at velocity v. The area of the loop increases as it travels to the right
• This equation is valid if B, l, v are mutually perpendicular. This EMF is called motional EMF
dx
Blvdt
dxlB
dt
dAB
dt
dLawsFaradayFrom B
|:'
Induced EMF in a Moving Conductor in a Magnetic Field
• The magnetic force on the
electrons on the rod is
given by:
where q is the charge on
the rod
• When the rod moves to the right with velocity v, electrons in the rod also move with this speed & feel the force
• Another approach to calculating the EMF, is to determine the work done to move a charge q, from one end of the rod to the other:
BvqF
vBlq
W
q
UisEMFThelqvBdFW
The Force Required to Move a Conducting Rod in a Uniform Magnetic Field
• To make the rod move to the right
an external force must be applied
in the direction of motion
• The power delivered to move the rod equal the power dissipated in the resistance of the rod.
R
vlBFext
22
R
lBv
RRIPP dispext
2222
Electric Generators (AC)
• A mechanically turned armature, consisting of N-loops of a coil wound on the armature
• As the armature is rotated, an EMF is induced in the rotating coil, which alternates as the magnetic flux through the loop reverses. The induced EMF is:
NBAwheretortNBA 00 sinsin
Electric Generators (AC)• The induced EMF is a sinusoidal voltage
• A typical AC Generator (Alternator):