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Aqa Gcse Physics > Paper 2 - Topic 7, Magnetism And Electromagnetism > Flashcards

Paper 2 - Topic 7, Magnetism And Electromagnetism Flashcards

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1
Q

What is an alternator

A

A device that makes use of the generator effect to generate alternating current

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2
Q

Define attraction

A

Opposite poles will experience a force of attraction, meaning they will experience a force towards each other, the force between a magnet and magnetic material and is always one of attraction

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3
Q

What happens when a current flows through a wire

A

A magnetic field is induced around it

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4
Q

What is a dynamo

A

A device that makes use of the generator effect to generate a direct current

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5
Q

What is an electric motor

A

A current carrying coil of wire in a magnetic field, the two sides of the coil that are perpendicular to the magnetic field experience forces in opposite directions causing rotations

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6
Q

What is an electromagnet

A

A solenoid with an iron core

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7
Q

What is Flemings Left hand rule

A

Force = thumb
Current = middle finger
Magnetic field = pointer finger

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8
Q

What is the generator effect

A

When there is a relative motion between an electrical conductor and a magnetic field, a potential difference will be induced across the ends of the conductor, a current will flow if this conductor is part of a complete circuit

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9
Q

What is an induced magnet

A

A material that becomes a magnet when it is placed in an existing magnetic field but loses its magnetism quickly once it is removed, always produce attractive forces

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10
Q

What are magnetic field lines

A

Lines representing the strength and direction of a magnetic field, the field line direction at any point is in the direction that a force would act on another North Pole if placed at that point

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11
Q

What is a magnetic field

A

The region around a magnet in which another magnet or magnetic material will experience a force

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12
Q

Give examples of magnetic materials

A

Iron, steel, cobalt and nickel

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13
Q

Describe a microphone

A

A device that uses the generator effect to convert the pressure variations of sound waves into variations in the electrical current of a circuit

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14
Q

What is the motor effect

A

When a current carrying wire is placed in a magnetic field, a force will be experienced between the wire and the magnet responsible for the field

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15
Q

What is a permanent magnet

A

A magnet that produces its own magnetic field

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16
Q

What is repulsion

A

Like-poles will experience a force of repulsion, meaning they will experience forces in opposite directions

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17
Q

What is a solenoid

A

A wire wrapped into the shape of a coil that has a strong and uniform magnetic field inside

18
Q

What is a step down transformer

A

A transformer that has a smaller potential difference in the secondary coil than in the primary core

19
Q

What is a step up transformer

A

A transformer that has a larger potential difference in the secondary coil than in the primary core

20
Q

What is the unit for magnetic flux density

A

Tesla

21
Q

What is a transformer

A

An iron core with a primary and secondary coil of wire wound around opposite ends

22
Q

What are the uses of magnetic fields

A
  • generating electricity= rotating a coil of wire through a magnetic field generates a current
  • compass = points in the direction of Earths magnetic north and shows the earths core is magnetic
23
Q

If something is 100% efficient what does that mean

A

Input power = output power

24
Q

What is induced potential

A

If a conductor or field move relative to each other, a potential is induced across the conductor

25
Q

Which way do field lines point

A

From north to south

26
Q

How do you increase the strength of a magnetic field

A

Use a greater current

27
Q

How do you create a weaker field

A

Greater distance from the wire

28
Q

How do you increase the strength of a solenoid

A

Have an iron core in the centre as it is easier for magnetic field lines to pass through than air

29
Q

What factors affect the strength of a solenoid

A
  • size of the current
  • length
  • cross sectional area
  • number of turns in the coil
  • using a soft iron core
30
Q

What happens when their is relative movement between a conductor and a magnetic field

A

A potential difference is induced across the conductor

31
Q

How do dynamic microphones work

A
  • they produce a current which is proportional to the sound signal
  • fixed magnet is at the centre and the coil of wire around the magnet is free to move
  • pressure variations in the sound waves cause the coil to move and as it moves current is induced in the coil
  • the current is then sent to a loudspeaker
32
Q

How do loudspeakers work

A
  • current flows into coil
  • the magnetic field from magnet and from current interaction causing the coil to move
  • the cone therefore moves
  • producing pressure variations making sound
33
Q

What does a magnetic compass contain

A

A small bar magnet that points in the direction of the Earths magnetic field

34
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
35
Q

If the direction of current in a current-carting site placed in a uniform magnetic field is reversed, what happens to the force

A

The direction of the force is reveresed

36
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

37
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
38
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

39
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
40
Q

Describe the makeup of a basic transformer

A

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

41
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

Aqa Gcse Physics (8 decks)

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