12) Magnetism & the Motor Effect

Question 1

What does magnetism describe?

Answer 1

The ability of magnets to attract and repel other magnets

Question 2

What poles do magnets have?

Answer 2

North pole

South pole

Question 3

What happens when like poles on a magnet are close together?

Answer 3

They repel

Question 4

What happens when opposite poles on a magnet are close together?

Answer 4

They attract

Question 5

What are the 3 pure metals that can be turned into magnets?

Answer 5

Iron
Nickel
Cobalt
(steel is not a pure metal)

Question 6

What are metals that can be turned into magnets called?

Answer 6

Magnetic materials

Question 7

What are properties of magnetic materials?

Answer 7

They don’t always act as magnets
Can be attracted but not repelled
Non-magnetic materials will never be attracted

Question 8

What type of magnets are always magnetic even when they are not near other magnets?

Answer 8

Permanent magnets

Question 9

What do permanent magnets produce?

Answer 9

Their own electric field

Question 10

When do magnetic materials temporarily become magnets?

Answer 10

When close to a permanent magnet

Question 11

What force is always between an induced magnet and a permanent magnet?

Answer 11

An attractive force

Question 12

What are induced magnets?

Answer 12

Magnetic materials that become magnets when they are in a magnetic field

Question 13

When will magnetic materials stop being a magnet?

Answer 13

When moved away from a permanent magnet

Question 14

What do permanent magnets induce in magnetic materials?

Answer 14

Temporary poles

Question 15

How do temporary poles align with permanent magnets?

Answer 15

So that the magnetic material is attracted to the permanent magnet

Question 16

What pole will be induced to a magnetic material if it is next to the north pole of a permanent magnet?

Answer 16

A south pole

Question 17

What type of magnetism is when a magnetic material temporarily becomes a magnet when it’s close to a permanent magnet?

Answer 17

Induced magnetism

Question 18

What are magnetic forces caused by?

Answer 18

Invisible magnetic fields

Question 19

What is a magnetic field?

Answer 19

The area around a magnet where another magnet or magnetic material feels a force

Question 20

What does the strength of a magnetic field depend on?

Answer 20

The distance from the magnet

Question 21

Where is the magnetic field of a magnet strongest?

Answer 21

At the magnet’s poles

Question 22

What do magnetic compasses contain?

Answer 22

Small bar magnets

Question 23

What do arrows on magnetic field lines show?

Answer 23

The direction of a magnetic field

Question 24

What direction do magnetic field arrows always point?

Answer 24

North pole to south pole

Question 25

What is the strength of a magnetic field at any point indicated by?

Answer 25

The density of the field lines at that point

Question 26

Where does a compass needle point to?

Answer 26

The direction of the Earth's magnetic field

Question 27

What provides evidence the core of the Earth is magnetic?

Answer 27

The magnetic field around Earth with poles at the North and South

Question 28

What magnetic pole is the Earth's geographical N-pole?

Answer 28

Magnetically south

Question 29

What type of magnet does the Earth's core behave as?

Answer 29

A bar magnet

Question 30

What do compasses that are mounted vertically show? (dipping compass)

Answer 30

The Earth's magnetic field enters the Earth at different angles in different places

Question 31

What colour is north on a bar magnet?

Answer 31

Red

Question 32

What colour is south on a bar magnet?

Answer 32

Blue

Question 33

What type of field does any electric current produce?

Answer 33

A magnetic field

Question 34

What are the magnetic field lines around a single conducting wire?

Answer 34

Circles

Question 35

What does the strength of a magnetic field created by an electrical current depend on?

Answer 35

Size of current | Distance from wire

Question 36

When gripping a wire with your right hand, what do your thumb and fingers show?

Answer 36

Thumb- direction of current | Fingers- direction of magnetic field

Question 37

What is a solenoid?

Answer 37

A loop of wire coiled into a cylindrical shape

Question 38

What are the magnetic field lines inside of a solenoid?

Answer 38

Parallel closely spaced lines

Question 39

What do the individual magnetic fields from each individual coil of a solenoid add up to create?

Answer 39

A strong almost uniform magnetic field around the coil

Question 40

What are the magnetic field lines outside of a solenoid?

Answer 40

Like a bar magnet, with a clear north and south pole

Question 41

Where is the magnetic field weaker in a solenoid?

Answer 41

Outside

Question 42

How does the strength of the magnetic field change for a straight wire?

Answer 42

Strongest closest to the wire

Question 43

How does the strength of the magnetic field change for a solenoid?

Answer 43

Inside- stong and uniform | Outside- decreases in strength the further away

Question 44

What changes the magnetic field strength for both solenoids and straight wires?

Answer 44

The size of the current

Question 45

What is the unit for magnetic field strength?

Answer 45

Magnetic flux density (B)

Question 46

What is magnetic flux density measured in?

Answer 46

Tesla (T)

Question 47

What is the equation for magentic force produced?

Answer 47

force produced = magnetic flux density x current x length of wire F = B x I x L

Question 48

What 3 things is the force on a wire in a magnetic field directly proportional to? (dependent on)

Answer 48

Strength of magnetic field Length of wire Current through wire

Question 49

Why do coils carrying an electrical current in a motor rotate in a magnetic field?

Answer 49

The current going up one side of the coil is flowing in the opposite direction to the current coming down the other side

Question 50

What does a split-ring commutator do every half-turn of a coil?

Answer 50

Reverse the direction of the current

Question 51

Why do split-ring commutators reverse the direction of the current?`

Answer 51

To ensure the current is always moving in the right direction to keep the coil rotating

Question 52

What 3 ways can increase the size of the turning force acting on a coil carrying a current?

Answer 52

Magnetic field strength Current through coil Number of coils in wire

Question 53

What happens to the direction of a magnetic field as the direction of current changes?

Answer 53

The magnetic field direction changes

Question 54

What do stationary magnets do to electromagnets inside coils with a changing current?

Answer 54

Repeatedly attract and repel the electromagnet

Question 55

How do electromagnets inside speakers create sound?

Answer 55

1) Change in current through coil changes magnetic field direction 2) Changing field direction attracts and repels electromagnet to stationary magnet 3) Speakers vibrate backwards and forwards 4) Sound waves are produced

Question 56

What is converted to sound waves by a speaker?

Answer 56

Electrical signal

Question 57

What does Fleming's left hand rule determine?

Answer 57

The direction of force in the Motor Effect

Question 58

What does each finger mean in Fleming's left hand rule?

Answer 58

First finger- direction of magnetic field Second finger- direction of current Thumb- direction of force (direction conductor would move)

Question 59

What is the motor effect?

Answer 59

A wire carrying a current creates a magnetic field

Question 60

What are electromagnets?

Answer 60

Solenoids containing iron cores

Question 61

What does the catapult experiment show?

Answer 61

A wire carrying a current in a magnetic field experiences a force

Question 62

What is the process of the catapult experiment?

Answer 62

When power supply is on a current flows in free wire causing it to move Swapping poles of the magnet will reverse free wire's direction of movement Swapping wires connecting to power supply reverses direction of current Reversing direction of current reverses direction free wire moves