ME6 - Electromagnetic induction Flashcards
What is electromagnetic induction?
The creation of a voltage in a wire which is experiencing a change in magnetic field
What is the dynamo effect?
Transforming kinetic energy into electrical energy (in a power station this kinetic energy is provided by turbines)
How can you get EM induction?
- When an electrical conductor moves through a magnetic field (cutting the magnetic field lines) causing the electrical conductor changes
How can you test EM induction?
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
What happens if the direction of movement is reversed?
The induced voltage/current will be reversed too
What three things can you increase to get a bigger voltage?
- The strength of the magnet
- The number of turns on a coil
- The speed of the movement
What is the difference between a simple electric motor and a generator?
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
What does AC generators do?
They rotate a coil in a magnetic field which produces a current
What is there construction similar to?
A motor
What happens as the coil spins?
A current is induced in the coil. The current changes direction every half turn
What do generators have instead of a split-ring commutator?
Slip rings and brushes to the contact doesn’t swap every half turn
What do CRO displays show?
An ac voltage - the faster the revolutions produce more peaks and higher overall voltage
How do power stations use ac generators?
They produce electricity - they get the energy needed to turn the coils or magnetic field in different ways
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
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
The magnet is released from a greater height. How does this affect the voltmeter. Explain your answer
The magnet will be moving faster so the induced voltage will be greater
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
(i) Reading decreases - less voltage
(ii) Reading increases - more voltage
(iii) Reading will be negative
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?
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
Why does the voltage change on a graph?
- Direction of magnet changes
- Amount of field lines cut changes
- Speed of magnet changes
(Any one of these answers)
