Magnets Flashcards
What is a bar magnet?
It is a bar surrounded by an invisible magnetic field
It has a north pole and a south pole
The magnetic field lines are drawn from the north pole to the south pole
What happens when you bring two magnets together?
Opposite poles with attract each other
Like poles will repel
What happens if you freely suspend a bar magnet?
It will align itself north /south with the Magnetic field of the Earth
What happens if you place iron close to a bar magnet?
- Iron isnt usually magnetised BUT if it is put near a magnet it statrts to behave like a magnet and develops a magnetic field
- Iron will be attracted to any magnetic pole north or south
Does the Earth have a magnetic field
Yes
What is an electromagnet?
It is a magnet which can be turned on and off
How does an electromagnet work?
It is made from a coil of insulated wire with a current passing through
The current can be turned on and off therefore so can the magnet
How can you test for the magnetic field of an electromagnet
Sprinkling with iron filings will show the magnetic field as they align along the field lines
OR
Using a plotting compass which points N/S along the field lines
How can you increase the strength of an electromagnet?
1 Increase the current
2. Increase the number of coils on the turns
3. Place a core of soft iron inside the coil
State one use of an electromagnet
Scrapyards have an electromagnet on a crane to lift cars about. They can turn the magnet on to lift the car and off to let it go
What is a relay?
A relay links two circuits together so that turning on on one circuit causes the other to turn on.
They are used to turn on a high current circuit using a low current one. The reason is to stop the user coming into contact with the high current circuit.
