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FaradayGenerators/
MotorsInduced Current
Lenz’s Law/ Changing B
Transformers
In 1822, Michael Faraday wrote a goal
in his notebook:
“Convert Magnetism
into Electricity”
A magnetic field can induce a
current.
Electromagnetic Induction
The conductor, which is often a
piece of wire, must be ________ to the magnetic lines of
force
Perpendicular
The direction of the induced current is dependent on the relative motion of
the coil with respect to the magnet.
The Generator Effect
State the 4th RHR… one used for Faraday’s
law.
-Outstretched fingers are magnetic field
-Extended thumb is direction wire moves
-Palm shows direction of current flow
Changes mechanical energy into
electrical energy.
Generator
Coil of wire around a soft iron core to concentrate
magnetic force
Armature
Changes electrical energy into mechanical
energy
Motor
When a generator is connected in a closed circuit; the
current flow is proportional to
the _______
Electromotive Force (EMF)
0.707 times the maximum voltage
Effective Voltage
Even though it is called a force, it is a potential difference and is measured in
volts.
Electromotive Force (EMF)
An induced EMF that resists the applied EMF
Back EMF
The formula for calculating EMF, also state what the
variables are.
vBLv is the velocity
B is the field strength
L is the length of the conductor
A permanent horseshoe magnet is mounted so that the magnetic
field lines are vertical. If a student passes a straight wire between the poles and pulls it
toward herself, the current flow through the wire is from left to right. Which is the N – pole of
the magnet?
The top
3 Ways to increase EMF:
Increase the velocity of the wire
Increase the length of the wire
Increase the magnetic field strength
We will use our ____ RHR
when dealing with Lenz’s law
Second
An induced current always flows in such a direction as to oppose
the motion that induced it.
Lenz’s Law
________ currents are generated to
stop the motion of the metal arm of a
sensitive scale.
Eddy
If a mechanical load is placed on
the motor, slowing it down, the back EMF is ______.
Reduced
The N-pole of a magnet is moved
toward the right end of a coil. The
direction of the induced current is?
Counter clockwise
The varying magnetic flux is carried through the core
to the secondary coil which induces a varying EMF in the secondary
coil. This is called ______________
Mutual Inductance
A step-up transformer increases voltage – the current in the primary
circuit is ______ than that in the secondary.
Greater
Upon what does the ratio of the EMF in the
primary of a transformer to the EMF in the secondary of the transformer depend?
The ratio of number of turns of wire in the primary to the number of turns of wire in
the secondary.
Transformer Formula
Vs/Ns = Vp/Np
Or
Ip/Is = Vs/Ns = Vp/Np
In a transformer, current is inversely
proportional to ______
Voltage
The power produced in the primary coil is
______ to the power produced in the secondary coil.
Equal