magnetism Flashcards
What are the 2 ends of a bar magnet called?
south pole and north pole
name two magnetic materials
iron and cobalt
What happens if you arrange 2 magnets with their north poles close to each
other?
they repel
How can you arrange 2 magnets so they attract each other?
place the opposite poles close together
What is a magnetic field?
The area around a magnet where magnetic objects feel a force
How can you find the shape of a magnetic field?
Use iron filings or plotting compasses
Name 2 electrical devices that use magnets.
generators and loudspeakers
why do compasses point north?
It’s in the earths magnetic field
Describe the shape of the Earth’s magnetic field.
Similar to the field around a bar magnet
Why are compass needles weighted at one end?
In most places the Earth’s magnetic field is not parallel to the surface
Which part of the Earth is responsible for its magnetic field?
the outer core
What is the difference between the North Pole and the north magnetic pole of the Earth?
earth spins around the north pole, compasses point to the magnetic north
What is an induced magnet?
an object that only turns into a magnet when it’s in a magnetic field if another magnet
Which way does a plotting compass’ needle point when being used to plot the magnetic field around a bar magnet
towards south
away from north
How does a magnetic field diagram show where the field is strongest?
where the lines are closest together
What is a uniform magnetic field?
A magnetic field with the same strength everywhere
how can you produce a uniform magnetic field?
using two flat magnets
What shape is the magnetic field around a wire with a current flowing through
it?
circular around the wire
What is an electromagnet?
a magnet made when current flows through a coil of wire
How can you create a magnetic field around a wire?
pass a current through it
Where is the magnetic field around a wire strongest?
closest to the wire
How can you increase the strength of the magnetic field around a wire?
increase the current
How can you change the direction of the magnetic field around the wire?
reverse the current
What is a solenoid?
A coil of wire with a current flowing in it / Another name for an electromagnet
Why is an electromagnet called a temporary magnet?
It’s only magnetic when a current is flowing: you can turn it off!
Describe the magnetic field inside a solenoid.
Strongest place, uniform, goes along the centre of the coil
Why is the magnetic field of a solenoid stronger along the middle than outside it?
The field from the two halves of the coil reinforce each other in the middle and oppose each other outside.
Describe the magnetic field between two flat magnets.
uniform
What is the motor effect?
A force produced when a current flows inside a magnetic field
How can we MAKE a magnetic field that can be turned on and off (temporary magnet)?
flow a current through a wire
In terms of poles, which way does a magnetic field go?
n to s
What is the name of the effect of a wire feeling a force if it has a current in it and it is in a magnetic field?
the motor effect
How is the wire with the current arranged compared to the magnetic field for it to feel the greatest force?
at right angles
What connects the motor to the external circuit?
split ring commutator
What are on the ends of the wires that touch this?
carbon brushes
Give 2 ways of increasing the strength of the motor effect.
increase current
increase strength of magnetic field
What does magnetic flux density measure?
strength of magnetic field
What are the units of magnetic flux density?
tesla
What happens when you move a wire in a magnetic field?
a current or voltage induced in the wire
