Section 6: Magnetism And Electromagnetism

Question 1

Describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field and describe the factors which affect the size of the induced voltage

Answer 1

This is a dynamo. A magnet spun around a coil. The magnetic field lines are broken by the conductor
This motion produces electricity

Question 2

Know and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer:

Answer 2

Primary Voltage/No. Primary Turns = Secondary Voltage/No. Primary Turns

Question 3

Know and use the relationship: input power = output power

Answer 3

VPIP = VSIS

Question 4

Understand that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it and describe the factors which affect the size of the induced voltage

Answer 4

When a conductor experiences a changing magnetic field a voltage is induced across the conductor
Id the conductor is part of a complete circuit a current in the circuit flows
To increase the induced voltage: increase the strength of magnet; move the conductor faster; increase the number of coils/conductors.

Question 5

Describe the properties of magnetically hard and soft materials

Answer 5

A magnetically hard material retains its magneticpropertiesfor a long period of time/permanently They are hard to demagnetise.
A magnetically soft material looses its magnetic properties almost as soon as it leaves a magnetic field.

Question 6

Understand the term ‘magnetic field line’

Answer 6

Magnetic field lines represent the shape and direction of a magnetic field.

Question 7

Understand that magnetism is induced in some materials when they are placed in a magnetic field

Answer 7

Some materials that are not magnetic can become one when they are in a magnetic field. This is because the magnetic field encourages its electrons to align and form poles

Question 8

Describe experiments to investigate the magnetic field pattern for a permanent bar magnet and that between two bar magnets

Answer 8

To track field lines you can use iron filings, which are magnetic materials, which will line up along the magnetic field. and you can use compasses which will show that the lines go from north to south. The following results will occur:

Question 9

Describe how to use two permanent magnets to produce a uniform magnetic field pattern.

Answer 9

hold two opposite poles close to each other so that they attract as this makes a uniform magnetic field’