Electromagnetism Flashcards
Magnetic field lines always point from
north to south.
The arrow on a magnetic field line shows
the direction the north pole of a compass would point if you placed it there.
A magnet placed near unmagnetised iron will
attract it, since iron is a magnetic material.
A magnet placed near unmagnetised steel will
attract it, since steel is a magnetic material.
A magnet placed near copper will
not attract or repel the copper. Copper is not a magnetic material.
Two north poles placed close together will
repel.
Two south poles placed close together will
repel.
A north pole and a south pole placed close together will
attract.
The ‘motor effect,’ describes how a wire feels a force if it is in a magnetic field and
it is carrying a current.
The ‘motor effect,’ describes how a wire feels a force if carries a current and
it is in a magnetic field.
Fleming’s left hand rule can be used to solve problems involving the ‘motor effect.’ What does the thumb represent?
Motion; in other words, the direction of the force on the wire.
Fleming’s left hand rule can be used to solve problems involving the ‘motor effect.’ What does the first finger represent?
The direction of the magnetic field, pointing from north to south.
Fleming’s left hand rule can be used to solve problems involving the ‘motor effect.’ What does the second finger represent?
The direction of the electric current, pointing from positive to negative.
What rule can be used to solve problems involving the motor effect?
Fleming’s left hand rule.
A current carrying coil of wire in a magnetic field experiences a force. (The ‘motor effect’) How could this force be increased? (4 ways)
Increase the current in the coil.
Add more turns to the coil.
Make each turn of the coil bigger.
Increase the magnetic field strength.
When a wire cuts through magnetic field lines a current is induced in it. How can the induced current be increased? (2 ways)
Move the wire faster.
Use a stronger magnetic field.
What rule can be used to work out the direction of magnetic field lines around a straight current-carrying wire?
The right hand grip rule.
The ‘generator effect’ describes how a current is induced when
a conductor cuts through magnetic field lines.
How can the magnetic field around a current carrying solenoid be increased? (4 ways)
Increase the current in the solenoid.
Add more turns to the solenoid.
Increase the area of each turn on the solenoid.
Add a soft iron core, turning the solenoid into an electromagnet.
How can the magnetic field around a current carrying electromagnet be increased? (3 ways)
Increase the current in the electromagnet.
Add more turns to the electromagnet.
Increase the area of each turn on the electromagnet.
What is a uniform magnetic field?
When the magnetic field lines are straight, parallel and equally spaced.
How can a uniform magnetic field be produced?
By bringing the north and south poles of two bar magnets close together. There will be a uniform magnetic field in the gap between them.
What is an example of a ‘hard’ magnetic material?
Steel.
What is a magnetic material?
A material that can be magnetised, i.e. turned into a magnet.
What does it mean if a magnetic material is described as ‘soft’?
The material is easily magnetised and demagnetised.
What is an example of a ‘soft’ magnetic material?
Iron.
What does it mean if a magnetic material is described as ‘hard’?
The material cannot be easily magnetised. Once magnetised, it is difficult to demagnetise.
How could the magnetic field between two magnets be strengthened?
Move them closer together.
