KICKSTART PHYSICS
MOTORS AND GENERATORS
1. THE MOTOR EFFECT
2. LENZ’S LAW
3. GENERATORS
4. TRANSFORMERS
5. AC INDUCTION MOTORS
Kickstart would like to acknowledge and pay respect to the traditional owners of the land – the
Gadigal people of the Eora Nation. It is upon their ancestral lands that the University of Sydney is built.
As we share our knowledge, teaching, learning, and research practices within this University may we
also pay respect to the knowledge embedded forever within the Aboriginal Custodianship of Country.
For more information head to
http://sydney.edu.au/science/outreach/high-school/kickstart/index.shtml
The University of Sydney
School of Physics
Motors and Generators
Generate Some Motor-vation
Risk Analysis
Conduct a risk analysis by filling out the following table.
List 3 risks to do with this investigation in the 2nd year lab. Also, list 3 risks in an industry where physics is used.
− What are the consequences of those risks? Use the risk matrix below to make your judgment.
− What precautions would you take to stop those risks from coming about?
− What steps would you take to mitigate those risks?
Risk
Consequence
Precaution/Mitigation
Kickstart
Physics
Industry
What sort of careers do you think you could get if you studied this topic at the University of Sydney?
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The University of Sydney
School of Physics
Motors and Generators
The Motor Effect
An electric charge experiences a force when it moves in a magnetic field. Thus, a current-carrying conductor
feels a force from a magnetic field. This is the motor effect.
Label the parts of the motor on the pictures below. Are these DC motors or AC? Or both? How can you tell?
Rotor
Stator
Power Source
Brushes
Commutator
Describe the application of the motor effect in the galvanometer and the loudspeaker.
Galvanometer
Loudspeaker
Features
(what is it
made of?)
Characteristics
(how does it
work?)
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The University of Sydney
School of Physics
Motors and Generators
Electromagnetic Induction and Lenz’s Law
Lenz’s Law
A changing ____________________ flux generates an ____________________ force, which induces a
____________________
that
produces
its
own
magnetic
____________________
that
____________________ the original change that caused it.
Predict
Observe
Apply
Magnet and
Coil
Falling Magnet
Jumping Rings
Pendulum
Arago’s Disc
This process of Predict, Observe, Explain, Apply was used by
David Unaipon (1872-1967), known as “Australia’s Leonardo
Da Vinci”. He was of the Ngarrindjeri people of South Australia
and was an Aboriginal inventor and author who made
significant contributions to science.
David invented many devices, including a sheep shearer that is
still in use today. He never received any recognition or
monetary benefit from any of his innovative inventions.
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The University of Sydney
School of Physics
Motors and Generators
Generators
AC/DC Generator
How can you tell if the generator is
producing AC or DC electricity?
Draw the output of the generator as
viewed on the DSO:
Twelve-Phase Generator
Draw what you think the output of the
generator would look like on the DSO:
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The University of Sydney
School of Physics
Motors and Generators
Transformers
Transformers use the ideas of electromagnetic induction
to transform one voltage into another. We can use
experimentation to determine the relationship between
the voltage and the number of turns in the coil.
Volts; Vs (V)
Number of Coils; Ns
First, we can count the number of turns in the coil; then
use the multimeter to measure the voltage.
What is the best way to represent this data?
Conclusion
From this graph, what can you say about the relationship between the voltage and number of turns in the
secondary coil?
How would you represent this mathematically?
Discussion
You have the relationship between the secondary voltage and coils. Calculate the relationship between the
primary voltage and coils:
𝑉!
=
𝑛!
Are they the same? Can you write a general expression for all 4 of these terms?
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The University of Sydney
School of Physics
Motors and Generators
AC Induction Motors
Construct from the parts provided a model
AC induction motor.
Write down your method for the construction of the models:
Calculate the synchronous speed:
𝑛! =
120׃
=
𝑝
where ƒ is the motor supply’s frequency in Hertz and 𝑝 is the number of magnetic poles.
Draw the output of the 2 phases on the Digital Signal Oscilloscope when they are 90° out of phase:
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The University of Sydney
School of Physics
Motors and Generators
Title ____________________________________________
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