3b.4 - Electromagnetic Induction Flashcards
What is electromagnetic induction?
The creation of a potential difference across a conductor which is experiencing a change in magnetic field
How can you induce a voltage? (3)
- Moving a magnet in a coil of wire
- Moving an electrical conductor in a magnetic field which
- Turning a magnet end to end in a coil
How do you reverse the current in electromagnetic induction? (2)
- Move the magnet in the opposite direction
- If the polarity of the magnet is reversed
How do you create an AC?
By keeping the magnet moving backwards and forwards
How do generators work? (3)
- A magnet turns and the magnetic field changes, which induces a current
- When the magnet makes it to half a turn, the direction of the magnetic field changes so current flows in the opposite direction
- This gives an AC current
What is an appliance that uses electromagnetic induction?
Dynamos
What do transformers do?
Change the potential difference
What are the features of a transformer? (4)
- Primary coil
- Iron core
- Secondary core
- AC supply
What do step up transformers do and what do they loom like?
- Increase voltage
- Less coils on primary coil than on secondary coil
What do step down transformers do and what do they look like?
- Decrease the voltage
- More coils on primary coil than on secondary
How do transformers work? (4)
- Primary coil produces a magnetic field which stays within the iron core so nearly all is passed through the secondary so not much is lost
- Because of AC in primary magnetic field in iron is constantly changing direction
- Felt by secondary
- Induces alternating potential difference
Why is the iron core laminated?
The core is layered to cut out induced currents in the iron layers
What would happen if the core wasn’t laminated?
The efficiency of the transformer would be greatly reduced
What would happen if you supplied DC to the primary coil?
You’d get nothing out of the secondary as there would be no induction
Where are switch mode transformers used?
Chargers
