Magnetism and Electromagnetism - Physics Paper 2

Question 1

What does a magnet have around it?

Answer 1

A magnetic field

Question 2

What is a magnetic field?

Answer 2

A region where magnets experience a force acting on them

Question 3

What type of force is a magnetic force?

Answer 3

A non-contact force

Question 4

What can a magnetic field be represented by?

Answer 4

A field diagram

Question 5

How many poles do magnets have?

Answer 5

2

Question 6

What are the 2 poles called?

Answer 6

North and South

Question 7

What do the arrows on magnetic field lines point to?

Answer 7

from north to south

Question 8

What do the direction of magnetic field lines show?

Answer 8

The direction of the force the north pole would feel if it was placed in that location

Question 9

The stronger the magnetic field at any point…

Answer 9

the closer together the field lines are

Question 10

What do like poles do?

Answer 10

Repel

Question 11

What do unlike poles do?

Answer 11

Attract

Question 12

What’s inside a compass?

Answer 12

A tiny bar magnet

Question 13

What are the 2 types of magnets?

Answer 13

Permanent and induced

Question 14

What do permanent magnets do?

Answer 14

They produce their own magnetic fields

Question 15

What are induced magnets?

Answer 15

Magnetic materials that turn into magnets when they’re in a magnetic field

Question 16

What happens when you take a magnetic field away from an induced magnet?

Answer 16

It loses its magnetism

Question 17

What are examples of permanent magnets?

Answer 17

Bar magnets and horseshoe magnets

Question 18

What are some examples of magnetic materials?

Answer 18

Iron, steel, nickel, cobalt

Question 19

What happens when a current flows through a wire?

Answer 19

A magnetic field is created around the wire.

Question 20

What is the right-hand thumb rule?

Answer 20

You use your right hand and point your thumb in the direction of the current, and curl your fingers. The direction of your fingers is the direction of the field

Question 21

The larger the current through the wire, or the closer to the wire you are…

Answer 21

the stronger the field is

Question 22

How can you increase the strength of the magnetic field that a wire produces?

Answer 22

by wrapping the wire into a coil called a solenoid

Question 23

How can you increase the magnetic field around a solenoid even further?

Answer 23

By putting a block of iron in the centre of the coil. The iron core becomes an induced magnet whenever current is flowing . The magnetic field of the core and the coil combine, making a stronger magnet overall.

Question 24

What is a solenoid with an iron core called?

Answer 24

An electromagnet

Question 25

Can electromagnets be switched on and off?

Answer 25

Yes

Question 26

What is the motor effect?

Answer 26

When a current-carrying wire in a magnetic field experiences a force

Question 27

How do you calculate the force on a wire carrying a current at right angles to a magnetic field?

Answer 27

force = magnetic flux density × current × length

Question 28

What are the units of magnetic flux density?

Answer 28

Tesla (T)

Question 29

What is magnetic flux density?

Answer 29

How many field (flux) lines there are in a region. This shows the strength of the magnetic field.

Question 30

If a current is flowing at 90 degrees to a magnetic field, how can you tell which way the force is acting on the conductor due to the motor effect ?

Answer 30

Using Fleming's left-hand rule

Question 31

How do you use Fleming's left hand rule?

Answer 31

Hold your thumb, forefinger and second finger at right angles to each other: - the forefinger is lined up with magnetic field lines pointing from north to south - the second finger is lined up with the current pointing from positive to negative - the thumb shows the direction of the motor effect force on the conductor carrying the current

Question 32

How can the speed of an electric motor be increased?

Answer 32

- By increasing the current | - By increasing the strength of the magnetic field

Question 33

The direction that a motor turns in can be found using Fleming's left hand rule and can be reversed either by....

Answer 33

- swapping the polarity of the dc supply | - swapping the magnetic poles over

Question 34

What allows loudspeakers to work?

Answer 34

The motor effect

Question 35

What is the generator effect?

Answer 35

The generator effect is the induction of a potential difference across a conductor which is experiencing a change in an external magnetic field

Question 36

Which ways can the potential difference across the ends of a conductor be induced?

Answer 36

- By moving the electrical conductor in a magnetic field | - By moving or changing a magnetic field relative to the electrical conductor

Question 37

How can induced potential difference be increased?

Answer 37

- Increasing the speed of the movement | - Increasing the strength of the magnetic field

Question 38

What do alternators do?

Answer 38

They generate an alternating current

Question 39

What do dynamos do?

Answer 39

They generate direct current

Question 40

What can you use an oscilloscope to see?

Answer 40

how potential difference generated in the coil changes over time

Question 41

What are microphones basically?

Answer 41

Loudspeakers in reverse that generate current from sound waves

Question 42

What are transformers?

Answer 42

Devices that can change the potential difference of an electrical supply using the generator effect.

Question 43

What is the structure of transformers?

Answer 43

They consist of 2 coils, the primary and secondary, wrapped around an iron core. Iron is used as a core because it magnetises and demagnetises quickly.

Question 44

Why is iron used as the core of transformers?

Answer 44

Iron is used as a core because it magnetises and demagnetises quickly.

Question 45

What are the 2 types of transformers?

Answer 45

The step down transformer and the step up transformer

Question 46

What happens in step-up transformers?

Answer 46

The number of turns on the secondary coil and the size of the pd across it are greater than across the primary coil.

Question 47

What happens in step-down transformers?

Answer 47

The number of turns on the secondary coil and the size of the pd across it are smaller than across the primary coil

Question 48

What is the transformer equation?

Answer 48

potential difference across primary coil / potential difference across secondary coil = number of turns on primary coil/number of turns n secondary coil

Question 49

potential difference across secondary coil X current in secondary coil =

Answer 49

= potential difference across primary coil X current in primary coil