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Physics > P7-Magnetism and Electromagnetism > Flashcards

P7-Magnetism and Electromagnetism Flashcards

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1
Q

What makes an object magnetic?

A

The domains can line up-the molecules’s electrons spin in the same direction

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2
Q

What poles attract?
What poles repel?

A
  • Opposite
  • Same
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3
Q

What are the magnetic materials?

A

Iron, Cobalt and Nickel

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4
Q

What is a magnetic field?

A

The region around a magnet

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5
Q

What is a permanent magnet?

A

A magnet that always produces a magnetic field and can’t be turned on or off

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6
Q

What is an induced magnet?

A

A magnet that can be magnetised when placed in another magnetic field

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7
Q

What are the characteristics of magnetic field lines?

A
  • Travel from north to south poles
  • Are more concentrated at the poles than elsewhere
  • Never cross-only loop around
  • Form rings
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8
Q

What direction does a current flowing through a wire produce its own magnetic field when veiwed from the direction the current is flowing and what tells us that the current is facing that direction on a diagram?

A
  • Clockwise
  • A cross
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9
Q

What direction does a current flowing through a wire produce its own magnetic field when veiwed from the the direction the current isn’t flowing and what tells us that the current is facing that direction on a diagram?

A
  • Anti-Clockwise
  • A dot
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10
Q

What direction does a current flowing through a wire produce its own magnetic field?

A

Clockwise-right hand rule

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11
Q

What is a solenoid and what does it produce?

A

A long coil of insulating wire-it produces a magnetic field

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12
Q

What is an electromagnet?

A

A soleniod with an iron core

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13
Q

What increases the strength of an electromagnet?

A
  • Increasing the current
  • Increasing the number of coils
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14
Q

What is the motor effect?

A

A wire carrying a current that creates a magnetic field that interacts with another magnet to cause a force that pushes the wire at right angles

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15
Q

How can the size of the motor effect force be increased?

A
  • By increasing the current
  • By using a stronger magnet
  • By increasing the length of the wire
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16
Q

How do you use Fleming’s left hand rule?

A

Thumb-Force
1st finger-Magnetic field
2nd finger-Current

17
Q

What is the formula for force on a wire in a magnetic field?

A

Force = magnetic flux density x current x length
F = BIL

18
Q

What are the units for magnetic flux density?

A

tesla, T

19
Q

What is magnetic flux density?

A

The strength of the magnetic field

20
Q

What causes the motor to keep spinning in the motor effect?

A

A split-ring commutator

21
Q

What current is used in an electric motor?

A

Direct current

22
Q

What can cause a current to be generated and what is this called?

A

A coil of wire being moved in relation to a magnet-this creates an induced current-called the generator effect.

23
Q

What factors reverse the current generated from a magnet?

A

If the magnet is moved back out of the coil
If the other pole of the magnet is moved into the coil

24
Q

How does an AC generator work?

A

A coil is rotated in the magnetic field inducing a current and brushes making contact between this wire and an external circuit causes an alternating current to flow in the external circuit

25
Q

How can the maximum current be increased in an AC generator?

A
  • Increasing the rate of rotation
  • Increasing the strength of the magnetic field
  • Increasing the number of turns on the coil
26
Q

How is a DC current produced by a generator?
What is the name for this generator?

A
  • By having a split ring commutator-however this produces a ‘lumpy’ current
  • Dynamo
27
Q

What do transformers do?

A
  • The increase the size of the voltage of an alternating current (step up transformer) while reducing the current)
  • They decrease the size of the voltage of an alternating current (step down transformer) while increasing the current)
28
Q

What causes a step up transformer?

A

If there are more turns in the secondary coil

29
Q

How do transformers work?

A
  • An AC power supply is supplied to the primary coil-this produces a magnet field that changes as the current changes
  • The iron core increases the strength of the magnetic field
  • The changing magnetic field induces a changing potential different in the secondary coil
  • The induced potential difference produces an alternating current in the electric circuit

Physics (8 decks)

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