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GCSE Physics > 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

poles of a 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 bought 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

● 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 most/all of its magnetism.

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8
Q

What is a magnetic field?

A

A region where other magnets or magnetic materials experience a non-contact force

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9
Q

Give four examples of magnetic materials

A

iron, steel, cobalt, nickel

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10
Q

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

A

It is always attractive

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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

The magnetic field strength decreases the further you move away.

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12
Q

In what direction does a magnetic field point?

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

What does a magnetic compass contain?

A

A small bar magnet that points in the direction of the Earth’s magnetic field.

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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
  • the magnitude of the current flowing through the wire
  • the distance from the wire
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16
Q

What is a solenoid?

A

A coil of wire which when current passes through creates a strong magnetic field.

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17
Q

Describe the magnetic field inside a solenoid

A

Strong and uniform

18
Q

What is an electromagnet?

A

A magnet consisting of a core, often made of soft iron that is temporarily magnetized by an electric current flowing through a coil that surrounds it

19
Q

What is motor effect?

A

When a force is exerted between a magnetic field and a current-carrying conductor 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 does the forefinger represent?

A

The forefinger points in the direction of the magnetic field.

22
Q

When using Fleming’s left hand rule what does the second finger represent?

A

The second finger points in the direction of current flow in the conductor.

23
Q

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

A
  • the magnitude of the current flowing through the conductor
  • the strength of the magnetic field that the conductor is placed in
24
Q

If the direction of current in a current-carrying wire placed in a uniform magnetic field is reversed, what happens to the force?

A

The direction of the force is reversed

25
Q

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

A

The conductor must be at right-angles to the magnetic field it is placed in.

26
Q

What is the unit used for magnetic flux density?

A

Tesla (T)

27
Q

How does electric motor work?

A

A simple electric motor can be built using a coil of wire that is free to rotate between two opposite magnetic poles. When an electric current flows through the coil, the coil experiences a force and moves.
The direction of the current must be reversed every half turn, otherwise the coil comes to a halt again. This is achieved using a conducting ring split in two, called a split ring or commutator. A coil of wire is used with lots of turns to increase the effect of the magnetic field.

28
Q

how do loud speakers make use of the motor effect?

A

The motor effect is used to convert variations in the current of an electrical circuit into the pressure variation which produce audible sound

29
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

30
Q

How is the pitch of the sound from a loudspeaker changed?

A

● The frequency of the a.c current is altered
● This creates a different frequency of vibration in the cone

31
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

32
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

33
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.

34
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

35
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 direct-current

36
Q

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

A
  • the generator effect
  • it converts the pressure variations in sound waves into alternating current in a circuit
37
Q

Describe the makeup of a basic transformer.

A

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

38
Q

Why is iron used as the core for a transformer?

A

It is easily magnetised

39
Q

Explain how a transformer works

A

● An alternating current flows through the primary coil
● This induces a changing magnetic field in the core
● This changing magnetic induces a current to flow in the secondary coil

40
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

41
Q

What can be said about the electrical power input and output of a 100% efficient transformer?

A

The electrical power input is equal to the electrical power output.

GCSE Physics (8 decks)

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