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physicsGCSE > p4 > Flashcards

p4 Flashcards

1
Q

what is the difference between permenant and induced magnets ?

A
  • permenant magnets have aligned magnetic domains
  • induced magnets have their magnetic domains alligned when in the prescence of a permenant magnet
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2
Q

what is the direction of a magnetic field?

How would you investigate this

A

north –> south
iron fillings experiment, shows attraction between the two

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3
Q

How does the behaviour of the dipping compass suggest that the earth’s core is magnetic ?

A
  • the earth behaves as a large bar magnet
  • magnet alligns with the earth’s magnetic field
  • points to geographic north pole, but mganteic south pole
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4
Q

what is the direction of the magnetic field around a current carrying wire?

A

right hand corkscrew rule

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5
Q

how do you show that a current carrying wire produces a magnetic field?

A

plotting compass

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6
Q

what does the strength of the magnetic field of a wire depend on?

A
  • the magnitude of the current (larger current=stronger field)
  • the distance from the wire (further away= weaker field)
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7
Q

how can a solenoid arrangment enhance the magnetic effect?

A
  • parallel loops make a coil, and their magneteic fields combine (add together) to produce a much stronger magnetic field
  • magnetic material can go inside core
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8
Q

how do a magnet and a current carrying wire exert a force on each other?

A
  • a current carrying wire’s has a magnetic field around it
  • field combines with permenant magnet
  • producing a force on the wire
  • (catapult field with stretched field lines)
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9
Q

describe flemming’s left hand rule?

A
  • Force
  • Field
  • Ccurrent
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10
Q

equation of force on conductor

A

F = B I L

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11
Q

How does the force exerted from a magnet and a current carying conductor, cause an electric motor to turn?

motor effect

A
  1. Both ends of the wire experience a force, causing them to move
  2. Once moved, because of the split ring commutator, there is no current, but the coil continues to turn because of it’s own momentum
  3. The direction of the coil and the commutator is reversed
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12
Q

Describe the role of the split ring commutator

A

Enables the current to flow the same way from the battery, but change to different halves of the coil as it spins. This makes sure that the force of the left hand side is always down wards and the force of the right hand side of the coil is always downwards

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13
Q

how can you chnage the speed of the motor?

A
  • magntitude of the current flowing in the coil
  • strength of the magnetic field
  • number of coils of wire
  • length of the coils
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14
Q

describe electro magnetic induction?

A
  • changing magnetic field around conductor (cuts field lines)
  • induces a p.d across the ends of a conductor
  • creating a current
  • generating a magnetic field that would oppose the original change
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15
Q

how would you increase the induced potential difference ?

A
  • move the wire faster
  • using a stronger magnetic field
  • using more wire (loops/coils)
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16
Q

how is the generator effect used in an alternator?

what type of current is produced?

A

a.c is produced
the coil of wire spins between poles of magnet, wire experiences a changing magnetic field …..
uses a slip ring

17
Q

How is the generator effect used in a dynamo?

what type of current does it produce?

A

d.c

18
Q

how does a transformer work?

alternating p.d in primary coil

A
  • alternating p.d in primary coil produces an alternating current in primary coil
  • a.c in primary coil produces a changing magnetic field in the iron core
  • this induces a changing p.d across the secondary coil
19
Q

how does a dynamic microphone work?

A

overall: convert pressure variations in soun waves into varations in current in elctrical circuits
1. sound waves create pressure waves, areas of high pressure (compressions) –> push diaphram in
2. areas of low pressure (rarefractions)–> push diagphram out
3. as the diaphram moves in and out, so does the coil, (experiencing a ching magnetic field)
4. a p.d is induced across the wire
5. current generated

20
Q

how do loudspeakers work?

A

overall: varations in current converted to variation in pressure varations in sound waves
1. changing p.d produces a changing current
2. curent produces a force on coil of wire , because is in a magnetic field
3. cone moves in and out
4. producing a sound wave

physicsGCSE (7 decks)

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