# P2 Electricity and magnetism pages 122-138 yr 8 Flashcards Preview

## Science > P2 Electricity and magnetism pages 122-138 yr 8 > Flashcards

Flashcards in P2 Electricity and magnetism pages 122-138 yr 8 Deck (74)
1
Q

What do doctors use to help keep a baby alive and how?

A

Doctors use an incubator to help keep a premature alive. an electric current flows through a heater that keeps the baby warm.

2
Q

What is current?

A

The current is the amount of charge flowing per second.

3
Q

What happens when you complete a circuit?

A

When you complete a circuit, charged particles or charges move in metal wires.

4
Q

What do need to do for the current to flow in a complete circuit?

A

When you press the switch on a torch the light comes on. The switch opens and closes a gap in the circuit. You need to close the gap and make a complete circuit for a current to flow.

5
Q

When people talk about electricity what do they usually mean?

A

When people talk about ‘electricity they usually mean ‘electric current.’

6
Q

How do you measure current?

A

You can measure current using an ammeter

7
Q

What is current measured in?

A

Current is measured in amps.

8
Q

What is amps shortened for?

A

Amps is shortened for amperes.

9
Q

What is the symbol for amps?

Give an example on how to use the symbol.

A

The symbol for amps is ‘A’ e.g. the current in the circuit 0.4 A.

10
Q

Where do the charges come from?

A

The cell or battery pushes charges around the circuit. The battery does not produce the charges that move. They were already there in the wires. In a metal the charged particles that move are electrons.

11
Q

How do you can build circuits? Using what?

A

You can build circuits using components such as batteries, bulbs and motors.

12
Q

Why do we use symbols instead of drawing each diagram as a picture?

A

It would take a long time to draw a picture of each circuit so you can use circuit symbols instead.

13
Q

What is a cell?

A

A cell is another word for a battery.

14
Q

What could be a reason for the circuit not working?

A

The cells might not be connected in the right way round.

15
Q

What do doctors use to start someone’s heart if it stops?

A

A doctor can use a defibrillator to start someone’s heart if it stops.

16
Q

What can defibrillators produce?

A

Defibrillators produce a large potential difference (sometimes called voltage), much bigger than a battery can produce.

17
Q

What does p.d. stand for and what is it?

A

The cell or battery provides the push to make the charges move. The push is called a potential difference which is what p.d. stands for.

18
Q

What can potential difference tell you about the force on charges?

A

The potential difference across a cell tells you about the size of the force on the charges.

19
Q

What does potential difference also tell you?

A

The potential difference also tells you how much the energy can be transferred to the components in the circuit by the charges.

20
Q

How does a potato produce a potential difference?

A

In a potato cell a chemical reaction between the metals and the potato produces a potential difference.

21
Q

How do you measure potential difference?

A

You measure potential difference by using a voltmeter which can be shortened to volts.

22
Q

What is the symbol for volts?

Give example of it can be used.

A

The symbol for volts is ‘V’. For example, the potential difference across the cell is 6V.

23
Q

What is a rating?

A

You can measure the potential difference of a cell by connecting a voltmeter across it. This is also called the ratting.

24
Q

What can you measure the potential difference with?

A

You can measure the potential difference across a component in a circuit using a voltmeter.

25
Q

What is a better word to sue instead of voltage?

A

Sometimes people talk about the voltage of a cell or a battery. It is better to talk about potential difference.

26
Q

How can you think of a battery?

A

You can think of the battery lifting up the charges.

27
Q

What is the difference between a parallel and series circuit?

A

In a series circuit there is only one loop whereas in a parallel circuit there is mor than one loop.

28
Q

Why are parallel circuits very useful?

A

Parallel circuits are very useful because if one bulb breaks, the other lights stay on. Each bulb is independent of the others.

29
Q

How can control each lamp separately?

A

You can control each lamp separately in a parallel circuit by adding a switch to each branch.

30
Q

What is the current in a series circuit?

A

In any circuit that is connected in series anywhere where you place the ammeter the current will have the same reading.

31
Q

What will happen if you add components to a series circuit?

A

If you add components to a series circuit the current will get smaller.

32
Q

What is the current in a parallel circuit?

A

In a parallel circuit each branch has the same current.

33
Q

What happens if you add another branch to a parallel circuit?

A

If you add another branch to a parallel circuit the current in the other branches stay the same but the total current increases.

34
Q

How can you use a rope to think of a series circuit?

A

You can use a rope model when you are thinking about different types of circuit. In the rope model:
The rope moves at the same speed everywhere.
As more people hold the rope, the rope moves more slowly.

35
Q

How can you use a rope to show how parallel circuits work?

A

There are more loops of rope.

All the loops are driven by the same ‘battery’ person

36
Q

What happens to the potential difference in a series circuit?

A

The potential difference across each component adds up to the potential difference across the battery.

37
Q

What happens to the potential difference in a parallel circuit?

A

The potential difference across each component is the same as the potential difference across the battery.

38
Q

What does each component have in a circuit?

A

Each circuit component has a different resistance.

39
Q

What does resistance tell us?

A

The resistance tells us how easy or difficult it is for the charges to pass through the component.

40
Q

What is resistance measured in?

A

Resistance is measured in ohms.

41
Q

What is the symbol for ohms?

A

The symbol for ohms

42
Q

What does the current depend on?

A

The current depends on the push of the battery and also the resistance of the component.

43
Q

What equation do you use to calculate current?

A

Current(A) =potential difference(V)

divided by resistance

44
Q

What equation can you use to calculate the resistance of a component?

A

Resistance =potential difference (V)

Current (A)

45
Q

What happens inside a wire?

A

Inside a wire the moving electrons collide with the atoms of the wire. They transfer energy, and the wire gets hot.

46
Q

Name a liquid that is magnetic.

A

Ferrofluid is a special liquid that is magnetic.

47
Q

What does a magnet have?

A

A magnet has a north pole and a south pole

48
Q

What do north poles _______ north poles?

A

Repel

49
Q

What do south poles _______ South poles

A

Repel

50
Q

What do South poles _______ North poles?

A

Attract

51
Q

What are the materials attracted to a magnet called?

A

Only certain materials are attracted to a magnet. They are called magnetic materials.

52
Q

Give some examples of some metals.

A

Iron is a magnetic material, and so is steel because steel contains iron. Cobalt and nickel are also magnetic.

53
Q

What is a magnetic field?

A

In an electric field there is a force on a charge. In a magnetic field there is a force on a magnet or a magnetic material.

54
Q

What are the two ways that you can find out the shape of a magnetic field?

A

Using plotting compasses, using iron filings.

55
Q

What does a wire with an electric current flowing through it have?

A

A wire with an electric current flowing through it has a magnetic field around it.

56
Q

How can you investigate the field?

A

You can investigate the field with a plotting compass.

57
Q

Describe the strength of a magnetic field with a single loop.

A

The magnetic filed around a single loop isn’t very strong.

58
Q

What will make the magnetic much stronger?

A

If you put lots of loops together to make a coil the field is much stronger.

59
Q

What is an electromagnet?

A

Putting lots of loops close together forms an electromagnet because it has a strong magnetic field.

60
Q

What is the shape of the magnetic field like?

A

The shape of the magnetic field is just like the shape of the magnetic field around a bar magnet.

61
Q

How can you turn an electromagnet off and on?

A

You can turn an electromagnet off and on by switching the current off and on.

62
Q

When is the magnetic field produced?

A

The magnetic field is only produced when the current is flowing in the wire.

63
Q

What do electromagnets usually have in the centre of the coil?

A

Electromagnets usually have a magnetic material in the centre of the coil, called a core.

64
Q

What does the core do to the electromagnet?

A

The core makes the electromagnet much stronger.

65
Q

What are most core made of?

A

Most cores are made of iron.

66
Q

Is iron easy to magnetise?

A

Yes iron is easy to magnetise but it loses its magnetism easily.

67
Q

Describe the magnetism of steel.

A

Steel is hard to magnetise but keeps its magnetism.

68
Q

What would happen if you had a steel core?

A

If you had a steel core in an electromagnet you could not turn the electromagnet off, because the steel would still be magnetic.

69
Q

How can you make electromagnets stronger?

A

The strength of an electromagnet depends on:
The number of turns, or loops, on the coil. More tuns of the wire will make a stronger electromagnet.
The current flowing in the wire. More current flowing in the wire will make a stronger electromagnet.
The type of core. Using a magnetic material in the core will make a stronger electromagnet.

70
Q

What are the two main differences between a permanent magnet and an electromagnet?

A

There are two main differences between permanent magnets and electromagnets.
You can turn an electromagnet on and off.
You can make electromagnets that are much stronger than permanent magnets.

71
Q

What is one difference between an electromagnet and a bar magnet?

A

Electromagnets need electricity, but bar magnets do not. Both have fields.

72
Q

Where are the field lines most concentrated around a bar magnet?

A

At both poles.

73
Q

The arrow on magnetic field lines shows them flowing in which direction?

A

From North to South

74
Q

What is an electromagnet?

A

A current flowing in a coil of wire acts like a magnet.