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Separate Science - Physics Paper 2 > Separate Physics - P7 Magnetism and Electromagnetism > Flashcards

Separate Physics - P7 Magnetism and Electromagnetism Flashcards

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1
Q

Name the three magnetic materials.

A
  • Iron
  • Cobalt
  • Nickel
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2
Q

What happens when two ‘like’ poles are brought together?

A

They repel each other

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3
Q

Is magnetism an example of a contact or non-contact force?

A

Non-contact force

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4
Q

What do you call a material that becomes magnetic when it is placed in the magnetic field of another magnet?

A

Induced magnet

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5
Q

Draw the magnetic field lines around a bar magnet.

A
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6
Q

What happens when two opposite poles are brought together?

A

They attract each other

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7
Q

Complete the diagram to show the directions that the plotting compasses will point.

A
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8
Q

Draw the magnetic field around an electromagnet.

A
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9
Q

What happens when a current flows through a wire?

A

A magnetic field is produced

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10
Q

Describe the magnetic field lines in the middle of an electromagnet.

A

Strong and uniform

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11
Q

Give three ways in which you can increase the strength of an electromagnet.

A
  • Increase the voltage
  • Increase the number of coils on the wire
  • Use a soft iron core in the middle
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12
Q

Higher Q. In Fleming’s left-hand rule, what do the following represent?

a) First finger
b) Second finger
c) Thumb

A

a) Field (North to south)
b) Current (positive to negative)
c) Movement

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13
Q

What is a coil of wire called?

A

A Solenoid

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14
Q

Give two advantages of an electromagnet over a permanent magnet?

A
  • You can turn an electromagnet on and off.
  • You can change the strength of the electromagnet
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15
Q

What causes the Earth to have a magnetic field?

A

Liquid iron in the Earth’s core

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16
Q

Higher Q. What is the motor effect?

A

A conductor carrying a current placed in a magnetic field causes the magnet and the conductor to exert a force on one another.

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17
Q

Separate Higher Q. What three things affect the size of the force on a conductor in a magnetic field?

A
  1. The magnetic flux density.
  2. The length of the conductor that’s in the magnetic field.
  3. The size of the current through the conductor.
18
Q

Separate Higher Q. In a loudspeaker or headphones, how is the frequency of the sound wave determined?

A

The frequency of the sound wave is the same as the frequency of the AC.

19
Q

Separate Higher Q. What two things could you do to induce a potential difference across the ends of a conductor?

A
  1. Move a magnet in and out of a coil of wire
  2. Moving a conducting wire inside a magnetic field
20
Q

Separate Higher Q. What type of current is generated by an alternator?

A

Alternating current - AC

21
Q

Separate Higher Q. Describe how loudspeakers and headphones work.

A
  • AC current is passed through a coil of wire.
  • The coil is wrapped around one pole of a magnet (e.g. South).
  • This is placed inside a magnet of the opposing pole (e.g. North).
  • A paper cone is attached to the coil of wire.
  • As the current alternates, this moves the paper cone out and in.
  • As the cone oscillates, this cause vibrations in the air outside the cone and hence a sound wave is produced.
22
Q

Separate Higher Q. What is the generator effect?

A
  • A potential difference induced across the ends of a conductor if the conductor moves relative to a magnetic field.
  • If the circuit is complete, a current will be induced.
23
Q

Separate Higher Q. Give two ways that you could increase the size of an induced potential difference/current.

A
  1. Increasing the speed of movement of the conducting wire relative to the magnetic field
  2. Increasing the strength of the magnetic field
24
Q

Separate Higher Q. What type of current is generated by a dynamo?

A

Direct current - DC

25
Q

Separate Higher Q. Describe how a microphone works.

A
  • The microphone’s diaphragm is attached to a coil of wire.
  • The coil of wire is wrapped around a permanent magnet of a particular pole (e.g. south).
  • This magnet and wire sit inside another magnet of opposing pole (e.g. north).
  • Sound waves vibrate the diaphragm causing the coil to move in and out.
  • A current is generated in the wire.
26
Q

Separate Higher Q. If a transformer was 100% efficient, what would the electrical power output equal?

A

The electrical power output would equal the electrical power input

27
Q

Separate Higher Q. What’s the relationship between the ratio of the number of turns on the primary and secondary coils and ratio of the potential difference of the primary and secondary coils?

A

The ratio of the number of turns on the primary and secondary coils is the same as the ratio of the potential differences of the primary and secondary coils.

28
Q

Separate Higher Q. Do loudspeakers and headphones use the motor effect or the generator effect?

A

The motor effect

29
Q

Separate Higher Q. What does a basic transformer consist of?

A

A primary and secondary coil wound on an iron core

30
Q

Separate Higher Q. Describe how a transformer works.

A
  • An alternating potential difference is applied across the primary coil.
  • The iron core magnetises then demagnetises due to the AC current.
  • This change in magnetic field induces a potential difference in the secondary coil.
  • If the secondary coil is connected to a complete circuit, a current will be induced.
31
Q

Separate Higher Q. Describe how an alternator works.

A
  • Coil of wire spins inside a magnetic field.
  • A current is induced in the coil.
  • Slip rings and brushes are used so the current remains alternating.
32
Q

Separate Higher Q. Do microphones use the motor effect or the generator effect?

A

The generator effect

33
Q

Separate Higher Q. Describe how a dynamo works.

A
  • Coil of wire spins inside a magnetic field.
  • A current is induced in the wire.
  • A split ring commutator swaps the connections every half-turn so the current stays in the same direction.
  • A direct current (DC) is produced.
34
Q

Separate Higher Q. Why is iron used as the core of a transformer?

A

Iron is easily magnetised

35
Q

Separate Higher Q. What type of transformer has more coils on the secondary coil than the primary coil?

A

Step-up transformer

36
Q

Separate Higher Q. What type of current are transformers used with?

A

Alternating Current

37
Q

Separate Higher Q. What type of transformer has more coils on the primary coil than the secondary coil?

A

Step-down transformer

38
Q

Separate Higher Q. If the frequency of revolutions of the generator was increased, how would this oscilloscope trace change?

A
  1. More peaks
  2. Higher peaks
39
Q

Separate Higher Q. What type of current does this oscilloscope trace show?

A

Direct Current

40
Q

Separate Higher Q. What type of current does this oscilloscope trace show?

A

Alternating current

Separate Science - Physics Paper 2 (4 decks)

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