SUMMARY
1. Define motor and generator.
A motor is a device which converts electrical energy to mechanical energy
(or motion).
A generator is a device which converts mechanical energy into electrical
energy.
2. What does the term “magnetic field” describe?
The region surrounding a magnet where magnetic effects can be detected.
A compass needle or an iron/steel object experiences a force in a magnetic
field. A magnetic field is a pattern of magnetic vectors.
3. The Right Hand Rule for Motors allows the 3-dimensional application of three mutually
perpendicular effects – what are they?
1) The magnetic vectors, 2) the direction the charge is moving, and 3) the
resulting force on the wire.
4. How are the Right Hand Rules for Motors and Generators alike?
They each depend on three mutually perpendicular factors: magnetic
vectors, moving charge and force on the charge in the wire.
5. How are the Right Hand Rules for Motors and Generators different?
They differ in their cause and effect and are opposites of each other.
Cause
MOTOR:
Charges moving through Sideways force on charges
a wire near a magnet,
makes wire move; motor
while a battery is attached turns
GENERATOR:
Wire moving near a
magnet, while the
crank is being turned
PASCO scientific
Effect
Sideways force makes
charges move through
wire
Teachers Resource Guide
T-288
6. It may feel very difficult to crank a generator when it is attached to a very low resistance
circuit. Explain this apparent contradiction.
See Activity 7.17. The pressure difference created by cranking the Genecon
in a low resistance circuit generates more current. More current through the
Genecon’s coils will cause a stronger force opposing rotation, making it
harder to crank the Genecon.
7. In some situations, the motor effect and the generator effect can occur simultaneously.
Cite at least one example.
See Activity 7.17 and 7.20. A Genecon placed in a circuit behaves as a motor
as current moves through it. As its crank is turning, however, it is also
acting as a generator which is producing opposing current.
PASCO scientific
Teachers Resource Guide
T-289