Magnetism Flashcards
Why are electromagnets useful
They can be reduced or increased
How does an electric bell work
When the switch is on the electromagnet becomes magnetised and the striker is attracted to the magnet and hits the bell , this breaks the contact and the striker draws back making contact again so the striker than hits the ball again
What is a relay switch
By turning on a small current the electromagnet is magnetised and attracts the iron armature which pushes the springy contacts together and starts the bigger circuit
What are magnetic materials
Steel iron nickel and cobalt
What are the strongest part of a magnet
The poles , most magnets have two poles , a North seeking pole and a south seeking pole
What is the domain theory of magnetism
Magnetic materials contain within its structure tiny cells called domains and mini molecular magnets exist inside these domains
In an unmagnetised piece of iron all the mini magnets within a particular domain point are in the Same direction but in each neighbouring domain they point in different directions meaning the magnetic effect of the domain cancels out , however in a magnetised piece of iron all the domains are lined up so their magnetic effects reinforce each other
What are magnetically soft and magnetically hard materials
Domains in some materials are very easy to put into and out of line , these materials are magnetically soft and are easy to magnetised and demagnetise like iron.
Some materials like steel are magnetically hard. Their domains are difficult to line up but once magnetised they will line up which is why steel is used for permanent magnets but cannot be used for electromagnets
Where is a magnetic field the strongest
Where the magnetic lines of force are close together
How can you reverse the direction of an electromagnetic field
By changing the direction of the current
How can you determine the size and strength of the magnetic field produced by a solenoid
The size of current flowing through the coil
The number of turns on the coil
Rapping the coil around a soft iron core
How do scrap yards sort metal
Huge electromagnets are used to shortage iron an magnetic objects from other materials , the electricity is turned on to pick materials up and then turned off to drop them
How can electromagnets be used in hospitals
MRI scans , to pull metal out of people
What is the motor affect
When a current flows in a indicator that is in a magnetic field , the conductor experiences a force , the force may be big enough to move the conductor . This effect is used in an electric motor
How can the force be increased
Increasing the current flow or adding more loops of wire
How do you change the force direction
Reversing the N and S and changing the magnetic field direction or reversing the current flow
