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Physics paper 2 > Magnetism and electromagnetism > Flashcards

Magnetism and electromagnetism Flashcards

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1
Q

At which part of a magnet are the magnetic forces strongest?

A

At the poles of the magnet

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2
Q

What happens when two magnets are brought close to each other?

A

They exert a force on each other

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3
Q

What type of force is exerted if two like poles of a magnet are brought near each other

A

A repulsive, non contact force

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4
Q

What type of force is exerted if two unlike poles of a magnet are brought near each other

A

An attractive, non contact force

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5
Q

What is the difference between a permanent magnet and an induced magnet?

A
  • Permanent magnet produces its own magnetic field
  • An induced magnet becomes magnetic when placed in a magnetic field
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6
Q

What type of force does induced magnetism always cause?

A

Force of attraction

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7
Q

What happens when an induced magnet is removed from a magnetic field?

A

the induced magnet loses all its magnetism

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8
Q

What is a magnetic field?

A

The region surrounding a magnet where another magnet or magnetic material experiences a non contact force

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9
Q

Give four examples of magnetic materials

A

Iron
Cobalt
Steel
Nickel

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10
Q

What can always be said about the force between a magnet and a magnetic field?

A

It is always an attractive force

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11
Q

How does the strength of a magnetic field alter as you move further away from the magnet producing it

A

Magnetic field strength decreases as you move further away

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12
Q

In what direction does a magnetic field point?

A
  • In the direction that a north pole would experience a force if placed in the field
  • Form the north seeking pole to the south seeking pole of a magnet
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13
Q

What does a magnet compass contain?

A

A tiny bar magnet
Points in direction of Earth’s magnetic field
Always point towards the south pole of a magnet

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14
Q

What is produced when current flows through a conducting wire?

A

A magnetic field is produced around the wire

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15
Q

What determines the strength of the magnetic field around a current-carrying wire?

A
  • Magnitude of the current flowing through the wire
  • Distance from the wire
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16
Q

What is a solenoid?

A

Coil of wire which when current passes through creates a strong magnetic field

17
Q

Describe the magnetic field found inside a solenoid

A

Strong and uniform

18
Q

What is an electromagnet

A
  • Solenoid with an iron core
  • iron core increases strength of magnetic field
19
Q

What is the motor effect

A

When a force is exerted between a magnetic field and a current-carrying wire placed in that field

20
Q

What rule is used to determine the force experienced due to the motor effect?

A

Fleming’s left hand rule

21
Q

When using Fleming’s left hand rule, what do the fingers represent?

A

Thumb - Direction of the force, which results in the motion
Forefinger - Direction of magnetic field
Middle finger - Direction of current flow in the conductor

22
Q

What factors affect the size of the force on a current carrying wire in a magnetic field?

A
  • Magnitude of current
  • Strength of magnetic field
23
Q

What happens to force on a current carrying wire when current is reversed?

A
  • Direction of the force is reversed
24
Q

What criteria must be met for the equation linking force, magnetic flux density, current and length to hold?

A
  • The conductor must be at right-angles to the magnetic field it is placed in
25
Q

Unit for magnetic flux density

A

Tesla (T)

26
Q

How does an electric motor work?

A
  • Coil of wire, carrying a current is placed in a magnetic field
  • The forces on the two sides perpendicular to the field experience forces in opposite directions
  • Causing a rotational effect
27
Q

How do loudspeakers make use of motor effect?

A
  • Used to convert variations in the current of an electrical circuit into the pressure variations which produce audible sound
28
Q

Explain how a loudspeaker works

A
  • A cone with a wire wrapped around it is connected to an a.c power supply and is placed in a permanent magnetic field
  • When current flows through the wire, it creates a second magnetic field which interacts with the permanent field
  • This produces a force which causes the cone to vibrate
29
Q

How is the pitch of a sound from a loudspeaker changed

A
  • Frequency of the a.c current is altered
  • This creates a different frequency of vibration in a cone
30
Q

What happens when an electrical conductor moves relative to a magnetic field?

A

A potential difference is induced across the ends of the conductor

31
Q

What happens to an electrical conductor when there is a change to the magnetic field that it is placed in

A

A potential difference is induced across the ends of the conductor

32
Q

What is the requirement for an induced potential difference to cause a current flow?

A

The conductor must form a closed loop or be part of a complete circuit

33
Q

What can be said about the direction of the magnetic field produced by an induced current?

A
  • The direction of the field is such that it opposes the change that induced the current
  • This change is either the movement of the conductor or a change to the field
34
Q

What are two ways that the generator effect is used to generate different types of current?

A
  • In an alternator to produce alternating current
  • In a dynamo to produce a direct current
35
Q

What electromagnetic effect does a microphone take advantage of and how?

A
  • The generator effect
  • Converts the pressure variations in sound waves into alternating current in a circuit
36
Q

Describe the makeup of a basic transformer

A

A primary coil and a secondary coil of wire wrapped around an iron core

37
Q

Why is iron used as the core for a transformer?

A

It is easily magnetised

38
Q

Explain how a transformer works

A
  • Alternating current flows through the primary coil
  • This induces a changing magnetic field in the core
  • This changing magnetic field induces a current to flow in the secondary coil
39
Q

Why must the current flowing through the primary coil of a transformer be alternating?

A
  • For current to be induced in the secondary coil, the magnetic field in the core must be continuously changing
  • For the magnetic field to be changing, the current in the primary coil must be alternating

Physics paper 2 (4 decks)

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