Download 3 - Induction and Motors Notes Handout

07/05/2017
Science 30 Unit B: Induction
and the Motor
Name: _________
Date: _________
Electricity and Magnetism – were initially two different studies. An observation by
___________ found they were connected.
Electric Current - the rate of flow of electrical charge where: I =
current (amps, A)
Orsted discovered that a ______________ in a wire produced a
___________________ field!
This magnetic field can interact with other magnetic fields to produce:
The Electric Motor
-made of 4 main parts:
1. _______________________
2. _______________________
3. ________________________
4. ________________________
1. The Magnetic Field
- all electric motors need an external magnetic field
- provided by a permanent magnet
- the magnet and the apparatus holding it is sometimes called the
stator
2. The Armature/Rotor
- a loop of current carrying wire
- often more than one loop to increase the overall force
- the loop is attached to the payload (what you want to spin...)
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07/05/2017
3. Brushes and
4. Split Ring/Commutator
- in order for the motor to keep spinning, the direction of the
current must reverse every half-rotation
- the split ring contains a gap that momentarily breaks the
circuit before allowing current to reverse
- the brushes provide a contact point between
the armature and the split ring
Generators
A generator is based on the idea of induction. Faraday discovered that just as a current carrying
wire in a magnetic field produced movement (a force), a moving wire with no current in a
magnetic field will produce its own current.
Note: induction (a moving wire in a magnetic field produces current) is the OPPOSITE of what
we have learned before (a wire with a current in a magnetic field will produce movement).
Two kinds of current can be generated: In alternating current (AC), the direction of the current
fluxuates back and forth many times per second (commonly 60 times per second, or at 60 Hz.)
Note that if we add a split ring commutator to the generator, the direction of the current remains
the same. This is called direct current (DC).
In direct current, the direction of current stays the same.
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