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GCSE Physics AQA > P15 - Electromagnetism 2️⃣✅ > Flashcards

P15 - Electromagnetism 2️⃣✅ Flashcards

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1
Q

What is an alternator?

A

A generator that generates alternating current

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2
Q

What is a dynamo?

A

A generator that generates direct current

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3
Q

What is an electromagnet?

A

An insulated wire wrapped round an iron bar that becomes temporarily induced when there is a current in the wire

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4
Q

What is electromagnetic induciton?

A

The process of inducing a potential difference in a wire by moving the wire so it cuts across/ through the magnetic flux/ field lines of a magnetic field

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5
Q

What is flemings left hand rule used for, how does it work & what is each finger representative of?

A

A rule that shows the direction of a force on a current carrying wire in a magnetic field according to the directions of the current and the field and vice versa. Used for motors

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6
Q

What is flemings right hand rule used for, how does it work & what is each finger representative of?

A

A rule that shows the direction of a force on a current carrying wire in a magnetic field according to the directions of the current and the field and vice versa. Used for generators

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7
Q

What is the corkscrew rule used for, how does it work & what is each finger representative of?

A

(RIGHT HAND) Used to display directon of conventional current/ magnetic field. Used for magnetic fields

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8
Q

What is the generator effect?

A

The production of potential difference using a rotating/moving magnet within a coil of wire/ magetic field

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9
Q

What is induced magnetism?

A

Mangetism of an unmagentised material by placing it inside a magnetic field - can only attract not repel

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10
Q

What is permanent magnetism?

A

Magetised materials that have a magnetic field and attract and repel materials

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11
Q

What is magnetic flux density?

A

A measure of the strength of the magnetic field, the higher the magnetic flux density, the more powerfull the magnet

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12
Q

What is the motor effect?

A

When a wire carrying a current creates a magnetic field which interacts with other magnetic fields causing a force

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13
Q

What are the units of magnetic flux density?

A

T, Teslas

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14
Q

What is a solenoid?

A

A long coil of wire that produces a magnetic field in and around the coil when there is a current in the coil

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15
Q

What is conventional current?

A

When current travels from positive to negative, anticlockwise

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16
Q

What does ANTS mean?

A

A lways
N orth
T o
S outh

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17
Q

What is the shorthand notation for current flowing into a page?

A
18
Q

What is the shorthand notation for current flowing out of a page?

A
19
Q

Label this dynamo (d.c. generator)/ motor

A
20
Q

List 3 ways in which you could increase the induced voltage/ potential difference of a generator

A
  1. Increase the current supplied/ bigger battery
  2. Increase the number of loops in the coil
  3. Increase the strength of the permanent magnet
  4. Increase the speed of rotation of the coil
21
Q

Why is iron used for electromagnets not steel?

A

Because it’s magnetcially soft and can be magnetised quicker than steel. It would be a temporary magnet but steel would remain magnetised

22
Q

Label this Alternator (a.c. generator)

A
23
Q

A step up transformer ________ the voltage/p.d. and ________ the current

A

A step up transformer increases the voltage/p.d. and decreases the current

24
Q

A step down transformer ________ the voltage/p.d. and ________ the current

A

A step down transformer decreases the voltage/p.d. and increases the current

25
Q

What material is used for the core of a transformer and why?

A

Iron because its easily magnetised

26
Q

What is the purpose of the core of a transformer?

A

To transfer the alternating magnetic field from the primary to the secondary coil

27
Q

Why do transformers have to be alternating current (a.c.)?

A

Because the current needs to be capable of changing to allow for transformers to step up/ step down current

28
Q

How does a step up transformer work?

A

There are more coils on the secondary coil so the p.d. induced on the secondary is greater than primary, consequently stepping up the voltage /p.d. and decreasing the current (distributing small current reduces heat lost in cables making it more efficient)

29
Q

How does a step down transformer work?

A

There are less coils on the secondary coil so the p.d. induced on the secondary is less than primary, consequently stepping down the p.d. and increasing the current back to as it was. Voltage/p.d. stepped back down to 230 for national gird distribution

30
Q

How does a transformer work?

A
  • Current supplied to transformer with the coil and iron core producing an alternating magnetic field
  • The magnetic flux/field is transferred through the iron core to the seconday coil
  • The coils on the secondary cut through the magnetic field in the iron core, consequently inducing a potential difference via electromagnetic induction
31
Q

What are loudspeakers?

A

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

32
Q

What are microphones?

A

Microphones detect vibrations caused by soundwaves and use the generator effect to convert them into electrical signals

33
Q

What type of current is used in microphones and loudspeakers?

A

Alternating current

34
Q

What is the function of a loudspeaker?

A

To convert electrical signals into sound waves

35
Q

What is the function of a microphone?

A

To convert sound waves into electrical signals

36
Q

Do loudspeakers rely on the motor effect or generator effect (electromagnetic induction)?

A

Motor effect

37
Q

Do microphones rely on the motor effect or generator effect (electromagnetic induction)?

A

Generator effect (electromagnetic induction)

38
Q

How do microphones work?

A
  1. soundwaves hit the diaphragm
  2. this causes the diaphragm and coil of wire to move
  3. as the wire moves withthin the magnetic field of the permanent magenet it will generate a current via electromagnetic induction (generator effect)
39
Q

How do loudspeakers work?

A
  1. An alternating current flows through the coil of wire and creates a magnetic field in the coil
  2. the magnetic field in the coil interacts with the magnetic field of the permanent magnet
  3. The interacting magnetic fields will exert a force on the coil (motor effect) causing it to move back and forth along the permanent magnet
  4. This causes the cone to change shape
  5. As the current is alternating (changing), the magnetic field and the force it experiences will also alternate; this means the coil of wire and cone rapidly move back and forth, oscillate, they vibrate
  6. these vibrations form the cone are so fast that they create pressure variations in the air - which are the sound waves
40
Q

What 4 metals are magnetised?

A
  • Iron
  • Steel
  • Nickel
  • Cobalt

GCSE Physics AQA (19 decks)

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