Paper 2 Knowledge Gaps: Content Flashcards

1
Q

What are the different types of generators?

A
  • alternators
  • dynamos
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2
Q

What current does an alternator produce?

A

Alternating current

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3
Q

What current does a dynamo produce?

A

Direct Current

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4
Q

What is the difference between the parts of an alternator and the parts of a dynamo?

A
  • alternators have slip rings and brushes
  • dynamos have split ring commutators
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5
Q

Describe how an alternator works

A
  • The coil of wire rotates relative to the magnets,
  • this induces a magnetic field in the coil
  • which then induces a voltage and current in the coil.
  • as the coil rotates faster, the peaks of the oscillation get larger and more frequent
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6
Q

What is the role of a slip ring in an alternator?

A
  • the contacts don’t swap every half turn
  • so an alternating current is produced
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7
Q

How do dynamos work?

A
  • As the coil of wire spins relative to the magnet, a magnetic field is induced
  • so, a voltage and current are induced in the coil.
  • as the coil rotates faster, the oscillations get larger and more frequent
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8
Q

What is the role of the split ring commutator in a dynamo?

A
  • contacts swap every half turn
  • so the current is always flowing in the same direction
  • producing a direct current
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9
Q

What do loudspeakers do?

A

Take electrical signals and use the motor effect to convert them into vibrations, which then generate sound waves

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10
Q

What do microphones do?

A

Detect vibrations caused by sound waves and convert them into electrical signals

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11
Q

What current do loudspeakers and microphones use?

A

alternating current

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12
Q

What effect do loudspeakers and microphones use?

A

Motor effect

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13
Q

How does a loudspeaker work?

A
  1. A.C. flows through wire and creates a magnetic field
  2. this magnetic field of the coil interacts with the magnetic field of the permanent magnet in the loudspeaker
  3. interacting magnetic fields exert a force onto the coil and cause it to move back and forth
  4. the cone will change shape
  5. as current is alternating, the magnetic field and the force experienced is also alternating, so the coil of wire and cone rapidly vibrate
  6. vibrations are so fast that the cone vibrations cause pressure variations in the air - sound waves are produced
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14
Q

How does a microphone work?

A
  1. sound waves hit the diaphragm
  2. diaphragm and coil of wire move
  3. wire is moving within the magnetic field of the permanent magnet = current generated
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15
Q

What determines the frequency and amplitude of the current produced in a sound wave?

A

the frequency and amplitude of sound waves

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16
Q

Describe the process that electricity goes through in the national grid?

A
  1. generated at power stations
  2. goes through a step up transformer
  3. goes through a bunch of wires and plyons
  4. goes to step down transformer
  5. then travels to our homes
17
Q

Why are step up transformers used in the national grid?

A
  • it increases the voltage to 400,000V
  • and minimises energy loss
18
Q

What is the role of step down transformers in the national grid?

A
  • decreases voltage to 230V
19
Q

Describe how transformers work

A
  1. alternating potential difference is applied across the primary coil
  2. causes a current to flow
  3. causing a magnetic field around the coil
  4. this induces a magnetic field in the iron core
  5. which induces a potential difference in the secondary coil
  6. which produces an alternating current
20
Q

Define moment

A

Rotational or turning effect of a force

21
Q

What is the equation for moment?

A

force x perpendicular distance from the pivot

22
Q

What are the units for moment?

A

Nm (Newton metres)