2 Electromagnets Flashcards
Magnet
A material with a magnetic field
Magnetic poles
The ends of a magnetic field, called north-seeking and south-seeking poles
Magnetic field
A region in which there is a force on a magnet or magnetic material
Magnetic force
Non-contact force from a magnet on a magnetic material
Magnetic field lines
Imaginary lines that show the direction of the force on a magnetic material
Permanent magnet
An object that is magnetic all of the time
What are the two ways in which you can find out the shape of a magnetic field?
- Using plotting compasses
- Using iron filings
Solenoid
Wire wound into a tight coil, part of an electromagnet
Electromagnet
A non-permanent magnet turned on and off by controlling the current through it
Core
Soft iron metal which the solenoid is wrapped around
Magnetise
To make a material magnetic
How can you make an electromagnet stronger?
- Increase the number of turns on the coil
- Increase the current flowing through the wire
- Using an iron core
True or false:
The strength of an electromagnet increases with distance
False
True or false:
The magnetic field around a solenoid has the same shape as a magnetic field around a bar magnet
True
Electric bell
A device that uses an electromagnet to make sound using a ‘make and break’ circuit
Circuit breaker
A device that uses an electromagnet to break a circuit if the current is too big
Loudspeaker
A device that uses an electromagnet to make a sound from a varying potential difference.
How does an electric bell work?
- The electromagnet attracts to the iron armature
- When the iron armature moves it breaks the circuit, so the current no longer flows
- The coil and core are no longer magnetic and the springy metal strip returns to its original position, and the bell rings once
- Now the circuit is complete again, so the armature moves and the bell rings again
How does a circuit breaker work?
- When a large current flows in the wire around the electromagnet, the magnetic field of the electromagnet is strong enough to attract the iron catch
- The catch moves down and this breaks the circuit
- The circuit stays off
- You can turn the device on again by pushing a reset switch
How do earphones work?
- Earphones contain tiny loudspeakers
- Electric current from phone flows in a coil of wire inside earphone
- Coil becomes an electromagnet that changes in strength
- A magnet inside the earphone attract and repel the electromagnet making the cone move in and out
- This makes sound
What are the differences between permanent magnets and electromagnets?
- You can then electromagnets on and off
- You can make electromagnets that are much stronger than permanent magnets
