KICKSTART PHYSICS MOTORS AND GENERATORS SCHOOL OF PHYSICS. Motors and Generators

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1 KICKSTART PHYSICS The University of Sydney MOTORS AND GENERATORS SCHOOL OF PHYSICS 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 own knowledge, teaching, learning, and research practices within this University may we also pay respect to the knowledge embedded forever within the Aboriginal Custodianship of For more information head to

2 Generate some motor-vation List three risks in the 2 nd year lab Risk Consequence Precaution Careers with Your demonstrator might be able to help with this. What sort of career do you think you could get if you studied this topic at the University of Sydney? Industry Research Public service

3 The University of Sydney 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: Features: Characteristics: Characteristics:

4 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. Magnet and coil Predict Observe Apply Falling magnet Jumping rings Pendulum Arago s disk David Unaipon Australia s Leonardo Da Vinci Ngarrindjeri people of South Australia. An Aboriginal inventor and author who made significant contributions to science. He used the process of Predict, Observe, Explain, Apply David invented many devices including a Sheep shearer still in use today. He never received any recognition or monetary benefit from any of his innovative inventions.

5 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:

6 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. First we can count the number of turns in the coil, then use the multimetre to measure the voltage. What is the best way to represent this data? Conclusion: Volts, V s (V) Number of coils, N s 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? Hint, it s a straight line. 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 of these 4 terms?

7 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 f p = where f 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 at 90 out of phase

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