What is the main energy transfer in an electric motor
Electrical energy to kinetic energy
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What is the purpose of the split-ring commutator in an electric motor
It reverses the direction of the current every half turn
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Why is a split-ring commutator needed?
To keep a DC motor turing in the same direction
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Two ways of increasing the strength of an induced magnetic field are...
Increase the electric current or use more turns of wire
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How is a magnetic field induced?
When current flows through a wire
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What does a circuit breaker do?
It disconnects the supply when there is too much current
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What is the purpose of a transformer?
To change the voltage of an AC supply. It can change high voltage to low voltage and vice versa.
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Explain the difference in coils for a step-up transformer
There will be more coils in the secondary coil than in the primary coil.
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Explain Fleming's Left-hand Rule
Magnetic field, direction of electric current and direction of force are all perpendicular. First finger is M, second finger is E, thumb is direction fo force.
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How does a loudspeaker use the motor effect?
A permanent magnet has an electromagnet coiled inside. Changing current causes the repulsion between magnets to continually change , causing cone to vibrate.
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How does a microphone use the motor effect?
Speech causes diaphragm to vibrate, causing coil to move through magnetic field to induce current.
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What is the generator effect?
Move a coil of wire in & out of a magnetic field. The movement must be perpendicular to the direction of the field.
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What is the motor effect?
When a current-carrying wire in the presence of a magnetic field experiences a force.
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Describe the structure of a transformer
Two coils of wire, a primary coil and a secondary coil, wound on an iron core. Iron is used as it is easily magnetised.
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If a magnetic field is moving left-right & the electric current is coming towards you, which direction is the force?
Up.
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What is the National Grid? Identify key parts of the system
System to transport electricty around the country. Has power stations, step-up & step-down transformers nd high-voltage transmission lines
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Other cards in this set
Card 2
Front
What is the purpose of the split-ring commutator in an electric motor
Back
It reverses the direction of the current every half turn
Card 3
Front
Why is a split-ring commutator needed?
Back
Card 4
Front
Two ways of increasing the strength of an induced magnetic field are...
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