ME6 - Electromagnetic induction Flashcards

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1
Q

What is electromagnetic induction?

A

The creation of a voltage in a wire which is experiencing a change in magnetic field

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2
Q

What is the dynamo effect?

A

Transforming kinetic energy into electrical energy (in a power station this kinetic energy is provided by turbines)

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3
Q

How can you get EM induction?

A
  • When an electrical conductor moves through a magnetic field (cutting the magnetic field lines) causing the electrical conductor changes
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4
Q

How can you test EM induction?

A

By connecting an ammeter to a conductor and moving the conductor through a magnetic field - it will show the magnitude and direction of the induced current

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5
Q

What happens if the direction of movement is reversed?

A

The induced voltage/current will be reversed too

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6
Q

What three things can you increase to get a bigger voltage?

A
  • The strength of the magnet
  • The number of turns on a coil
  • The speed of the movement
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7
Q

What is the difference between a simple electric motor and a generator?

A

Motor - you have a current in the wire and magnetic field which causes movement

Generator - You have a magnetic field and movement which induces a current

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8
Q

What does AC generators do?

A

They rotate a coil in a magnetic field which produces a current

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9
Q

What is there construction similar to?

A

A motor

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10
Q

What happens as the coil spins?

A

A current is induced in the coil. The current changes direction every half turn

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11
Q

What do generators have instead of a split-ring commutator?

A

Slip rings and brushes to the contact doesn’t swap every half turn

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12
Q

What do CRO displays show?

A

An ac voltage - the faster the revolutions produce more peaks and higher overall voltage

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13
Q

How do power stations use ac generators?

A

They produce electricity - they get the energy needed to turn the coils or magnetic field in different ways

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14
Q

A magnet is held above a coil. The coil is connected to a voltmeter. The magnet is released and falls into the coil

Explain why the voltmeter records a reading

A

As the magnet falls through the coil, there is a changing magnetic field acting on the coil. This inducers a voltage across the coil and a current through it

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15
Q

The magnet is released from a greater height. How does this affect the voltmeter. Explain your answer

A

The magnet will be moving faster so the induced voltage will be greater

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16
Q

State how the voltmeter reading changes when the same magnet?

(i) moves more slowly into the coil
(ii) moves into a coil with more turns
(iii) is reversed so that the S pole enters the coil first

A

(i) Reading decreases - less voltage
(ii) Reading increases - more voltage
(iii) Reading will be negative

17
Q

A student investigates how to produce a voltage. He hangs a magnet from the spring, above a coil that is connected to a data logger. The student pulls the magnet through the coil then releases it

Explain why the data is varied?
How do you know it is an alternating current?

A

1) The magnetic field is being cut forcing the amplitude to decrease as the spring with the magnet attached, slows down gradually
2) It goes from positive to negative

18
Q

Why does the voltage change on a graph?

A
  • Direction of magnet changes
  • Amount of field lines cut changes
  • Speed of magnet changes

(Any one of these answers)