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physics paper 1 > P4 > Flashcards

P4 Flashcards

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1
Q

What poles do all magnets have?

A

North and south poles.

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2
Q

What is a magnetic field?

A

A region where magnetic material (like iron, nickel, or cobalt) experiences a force.

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3
Q

How are magnetic field lines used in diagrams?

A

They show the direction and strength of the magnetic field, flowing from north to south outside the magnet.

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4
Q

What does it mean if magnetic field lines are close together?

A

The magnetic field is stronger.

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5
Q

What is magnetic flux density

A

It is a measure of the strength of the magnetic field, in teslas (T).

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6
Q

How do two permanent bar magnets affect each other’s magnetic fields?

A

When placed near each other, they create a combined magnetic field pattern.

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7
Q

How can you use iron filings to see a magnetic field pattern?

A

Sprinkle iron filings around a magnet, and they gather along the field lines, showing the magnetic pattern.

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8
Q

How does using a compass help you see a magnetic field pattern?

A

Place a compass near the magnet; the needle aligns with the magnetic field direction, helping trace the field lines.

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9
Q

What can you do to create a permanent record of a magnetic field pattern using paper and iron filings?

A

Place paper over the magnet, sprinkle filings, and tap gently. Use glue to fix the pattern for a permanent visual.

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10
Q

Describe the plotting compass method for mapping out a magnetic field.

A

Move a plotting compass around the magnet, marking the needle’s position at each point to draw the magnetic field lines.

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11
Q

Why is it difficult to remove all traces of a magnetic field from iron filings after removing the magnet?

A

filings retain some magnetism, creating a “memory” of the field pattern even after the magnet is removed.

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12
Q

How can you prove the Earth has a magnetic field using a compass?

A

Compasses always point north-south even when far from other magnets, showing that Earth has its own magnetic field

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13
Q

What happens when like poles of two magnets are brought near each other?

A

They repel each other.

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14
Q

What happens when opposite poles of two magnets are brought near each other?

A

They attract each other

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15
Q

How does a material become magnetized by a nearby magnet?

A

A magnetic material becomes a temporary magnet when near a magnet, aligning with the field, but loses magnetism when the field is removed.

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16
Q

What happens when an unmagnetized material is placed in a strong magnetic field?

A

It can become magnetized, temporarily or permanently, depending on the material.

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17
Q

How does the distance between two magnets affect their force of attraction or repulsion?

A

The closer they are, the stronger the force; the force decreases quickly with increased distance.

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18
Q

Why might two magnets attract or repel even when one is not visibly magnetic?

A

An unmagnetized material can be temporarily magnetized by a nearby magnet, creating attraction or repulsion.

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19
Q

How does a current-carrying wire affect its surroundings?

A

It produces a magnetic field around it.

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20
Q

What happens to the magnetic field when you increase the electric current through a wire?

A

The magnetic field strength increases.

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21
Q

What is the shape of the magnetic field around a straight, current-carrying wire?

A

Concentric circles form around the wire.

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22
Q

How can you determine the direction of the magnetic field around a current-carrying wire?

A

Use the right-hand rule: if you point your thumb in the direction of the current, your fingers curl in the direction of the magnetic field.

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23
Q

What happens to the magnetic field strength as you move further from the current-carrying wire?

A

The field strength decreases.

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24
Q

How does the magnetic field around a flat circular coil resemble that of a bar magnet?

A

The magnetic field in the center of the coil resembles the field around a bar magnet, with circular field lines around the coil.

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25
Q

What is a solenoid, and what is its magnetic field like?

A

A solenoid is a coil of wire with a strong, uniform magnetic field inside, similar to a bar magnet.

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26
Q

How can the magnetic field strength of a solenoid be increased?

A

Increase the current, add more turns to the coil, or insert an iron core.

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27
Q

How does inserting an iron core affect the magnetic field of a solenoid?

A

It increases the strength of the magnetic field and makes the solenoid an electromagnet.

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28
Q

What factors increase the magnetic effect at the ends of a solenoid?

A

Higher current, more turns in the coil, and the presence of an iron core.

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29
Q

What happens when a current-carrying conductor is placed in a magnetic field?

A

The magnetic fields from the wire and the magnets combine, resulting in a force on the wire.

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30
Q

Under what condition does a current-carrying wire experience no force in a magnetic field?

A

If the wire is aligned along the magnetic field lines, it won’t experience any force.

31
Q

How can the force on a current-carrying wire be increased?

A

By increasing the current, using a stronger magnetic field, or adjusting the angle of the wire so it is perpendicular to the magnetic field lines.

32
Q

How does the angle of the wire relative to the magnetic field affect the force it experiences?

A

The force is strongest when the wire is at a 90° angle to the magnetic field and weakens as the angle decreases.

33
Q

In which direction does the force act on a current-carrying conductor in a magnetic field?

A

The force acts perpendicular to both the direction of the current and the magnetic field

34
Q

How is a horseshoe magnet typically used to demonstrate this force?

A

The wire is placed between the poles of the horseshoe magnet, where the magnetic field is strong, causing the wire to experience a force when current is applied.

35
Q

What is Fleming’s left-hand rule used for?

A

It is used to find the direction of the force on a current-carrying conductor in a magnetic field.

36
Q

How do you apply Fleming’s left-hand rule?

A

. First finger points in the direction of the magnetic field (from north to south).
• Second finger points in the direction of the current (from positive to negative).
• Thumb points in the direction of the force (motion).

37
Q

What does magnetic flux density (B) represent in this formula?

A

It is a measure of the strength of the magnetic field.

38
Q

Why should you remember that magnetic flux density is just a fancy term for magnetic field strength?

A

It simplifies your understanding of

39
Q

How does a simple electric motor work with a current-carrying coil?

A

The coil is placed between opposite poles of a magnet, and the forces on each side of the coil cause it to spin on its axis.

40
Q

Why does the coil in an electric motor continue rotating in one direction?

A

A split-ring commutator reverses the current every half-turn to keep the motor rotating in the same direction.

41
Q

How can you increase the speed of a simple electric motor?

A

Increase the current, use a stronger magnetic field, or increase the magnetic flux density.

42
Q

How can Fleming’s left-hand rule help determine the rotation direction in a motor?

A

Draw arrows for the magnetic field and current directions on each side of the coil, and use Fleming’s left-hand rule to check if it will rotate clockwise or counterclockwise.

43
Q

How does a loudspeaker produce sound using a coil and a magnet?

A

A current flows through the coil, creating a magnetic field that interacts with the magnet’s field, causing the coil to move.

44
Q

What happens when the current in a loudspeaker coil changes direction?

A

The direction of the force on the coil reverses, causing it to move back and forth.

45
Q

How does the movement of the coil in a loudspeaker produce sound?

A

The moving coil makes a cone vibrate, creating sound waves in the air.

46
Q

What causes the pitch of the sound produced by a loudspeaker to change?

A

Variations in the frequency of the electrical current change the speed of cone vibrations, producing different sounds.

47
Q

How can a potential difference be induced in a conductor?

A

A potential difference is induced when a conductor cuts through magnetic field lines, or when there is a change in the magnetic field around a conductor.

48
Q

What is electromagnetic induction?

A

Electromagnetic induction is the process of inducing a potential difference in a conductor due to a changing magnetic field.

49
Q

What happens if the conductor is part of a complete circuit?

A

If the conductor is part of a complete circuit, a current is induced, generating electricity

50
Q

How can the size of the induced potential difference be increased?

A

Increase the speed of movement, use a stronger magnet, or increase the number of turns on the coil.

51
Q

What happens to the direction of the induced current if the movement direction or magnetic field polarity is reversed?

A

The direction of the induced current also reverses.

52
Q

What happens when the conductor cuts through the magnetic field lines faster?

A

A larger potential difference is induced.

53
Q

How does a microphone use electromagnetic induction?

A

Sound waves hit the diaphragm, causing it to move. The coil of wire attached to the diaphragm moves in the magnetic field, inducing a current that varies with the sound wave’s frequency and amplitude.

54
Q

What varies with the frequency and amplitude of the sound wave in a microphone?

A

The induced current.

55
Q

How does a dynamo generate direct current (DC)?

A

A dynamo has a coil that rotates in a magnetic field, inducing a potential difference in the coil. The split-ring commutator ensures the current flows in one direction, producing direct current.

56
Q

What type of current does a dynamo produce?

A

Direct current (DC).

57
Q

What component ensures the current flows in one direction in a dynamo?

A

The split-ring commutator.

58
Q

How does an alternator generate alternating current (AC)?

A

An alternator uses a rotating coil in a magnetic field with slip rings that allow the current to alternate as the coil spins, producing AC.

59
Q

What type of current does an alternator produce?

A

Alternating current (AC)

60
Q

What is the role of slip rings in an alternator?

A

Slip rings allow the current to alternate, producing an AC output.

61
Q

How can you determine the direction of current in the coil of a dynamo or alternator?

A

Use Fleming’s right-hand rule.

62
Q

What is a transformer used for?

A

To change the potential difference of an alternating current.

63
Q

How does a transformer work?

A

An alternating current in the primary coil creates a changing magnetic field in the iron core, which induces an alternating potential difference in the secondary coil.

64
Q

Why do transformers require alternating current?

A

An alternating current is needed to create a changing magnetic field, which is essential for inducing a potential difference in the secondary coil.

65
Q

What are the main components of a transformer?

A

Primary coil, secondary coil, and an iron core.

66
Q

Why is an iron core used in transformers?

A

To increase the strength of the magnetic field.

67
Q

What is a step-up transformer?

A

A step-up transformer increases the potential difference, with more turns on the secondary coil than on the primary coil.

68
Q

What is a step-down transformer?

A

A step-down transformer decreases the potential difference, with fewer turns on the secondary coil than on the primary coil.

69
Q

Why are step-up transformers used in power stations?

A

To increase the potential difference, reducing energy loss during transmission over long distances.

70
Q

Why are step-down transformers used in homes?

A

To reduce the potential difference to a safer level for domestic use.

71
Q

Why does a complete circuit need to be present for current to be induced?

A

Without a complete circuit, electrons cannot flow, and thus no current is produced even if a potential difference is induced.

72
Q

What does increasing the speed of the coil’s rotation do in a generator?

A

It increases the potential difference and the frequency of the alternating current produ

73
Q

What is the role of alternating current (AC) in transformers?

A

AC allows the magnetic field to constantly change, which is necessary for inducing a potential difference in the secondary coil.

physics paper 1 (4 decks)

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