P7 - Magnetism and Electromagnetism

Which pole will a plotting compass always point to?

South

Define magnet

Any material that produces a magnetic field

Define magnetic material

Any material that can be influenced by a magnetic field and has a potential to become a magnet

Define permanent magnet

Produces its own magnetic field all the time

Define induced magnet

Only has a temporary magnetic field

Name some magnetic materials

Nickel, Iron, Steel, Cobalt

How can a magnet become induced?

A magnetic material is placed in the field of a permanent magnet and it develops its own attractive magnetic field

What is the force between a permanent and induced magnet?

attractive

Define magnetically soft

Loses magnetism quickly

Name some magnetically soft materials

Nickel and iron

Name a magnetically hard material

Steel

What is a magnetic field?

The area of magnetic force around a magnet

What is the motor effect?

When a current-carrying wire in the presence of a magnetic field will experience a force

What happens when a current carrying wire is placed between a North and South pole?

the magnetic fields interact and the wire will experience a force

What position must the wire be at to experience the full force?

90' to the magnetic field

What does the thumb represent in Fleming's left hand rule?

direction of force

What does the index finger represent in Fleming's left hand rule?

magnetic field

What does the middle finger represent in Fleming's left hand rule?

current

What rule is used for the motor effect?

Fleming's Left Hand rule

What is magnetic flux density?

A measure of the strength of a magnetic field

What are the three ways that speed of rotations can be increased?

1. Increase current,

2. Add more turns to the coil,

3. Increase magnetic flux density

What device fixes the fact that a motor will never turn 360'?

split ring commutator

What does a split ring commutator do?

Swaps the direction of current every half turn so it the coil rotates in the same direction

If a wire experiences a change in magnetic flux...

a potential difference will be induced across it

A wire moving up and down repeatedly perpendicular to a magnetic field will:

generate an alternating potential difference

What three ways can we change the size of the pd induced (generator effect)?

1. Change strength of magnetic field,

2. Move wire faster across the field lines,

3. Shape the wire into a coil/more turns added

How are induced magnets made?

A magnetic material is put in the field of a permanent magnet