Magnetism and electromagnetism

What is a magnetic field

A region where magnetic materials experience a force. Magnetic field is strongest at poles

What are magnetic field lines

They shows the size and direction of magnetic fields and they point from North to South

What is uniform magnetic field

An area of constant magnetic field strength found directly in between two opposite poles

Magnetic materials

Cobalt, Nickel, Iron and Steel

Hard and Soft materials

Hard:

• Always has a magnetic field around them

• Can attract/repel other magnets

Soft:

• Only magnetic when in a magnetic field

• Can only attract magnets materials not repel them

• Loses it magnetism quickly

Magnetic field lines with iron fillings

• First, place paper over a magnet

• Next, sprinkle iron fillings onto the paper

• Then, gently tap the paper and the iron fillings shape themselves into an magnetic field

Magnetic field lines with compasses

• Place a magnet on top of paper and and draw an outline of the magnet

• Place a compass near the magnet and draw a dot where the red arrow is facing and the same for the other end of the arrow

• Keep repeating until you reach the other pole

Induced Magnetism

• When a magnetic materials brought near to a magnet that materials acts as a magnet

• This magnetism has been induced by the original magnet

• The closer the magnet and the magnetic materials, the stronger the induced magnetism will be

If the magnetic materials faces a North Pole the point it faces the magnet will acts a South Pole

Electromagnets

A solenoid with an iron core.

Ways to increase the strength of an electromagnet

• Increasing the voltage

• Increasing the number of coils

• Inserting an iron core

The motor effect

How to make it move with more force

Make it move in different directions

When a current-carrying wire is put between magnetic poles. The two magnetic fields affect each other and the wire moves.

Make it move with more force:

• Use a stronger magnet

• Increase the voltage

Make it move in a different directions

• Reverse the polarity of the magnets

• Reverse the direction of the current

What is the role of brushes in electric motors

The allow the coil to spin without the wires being tangled prevent the circuit from being damaged

What is the role of the split- ring commutator

It reverses the direction of the current which reverse the direction of the force on each side of the coil