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IGCSE Physics > Magnetism > Flashcards

Magnetism Flashcards

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1
Q

List magnetic materials

A

Iron
Steel
Nickel
Cobalt

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2
Q

What are ferromagnetic materials?

A

Iron

Steel

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3
Q

Give an example of a hard magnet material

A

Steel

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4
Q

What does a hard magnetic material mean?

A

Hard to magnetize- long time to magnetize

Permanent magnet

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5
Q

What does a soft magnetic material mean?

A

Easy to magnetise- short time to magnetize

Temporary magnet

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6
Q

Why are some materials attracted to magnets?

A

Because of the existence of tiny magnets inside. When a magnetic is brought near it, its tiny magnets are arranged uniformly

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7
Q

How can magnetism be made?

A

By induction
By stroking
By electrically

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8
Q

How can you magnetise electrically?

A

Place magnetic material in a solenoid connected to dc current

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9
Q

How can magnetism be destroyed?

A

Hammering a magnet
Heating
Dropping a magnet
Demagnetising by using reduced AC through a coil of wire wrapped round a magnet

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10
Q

What is the magnetic field?

A

The area around a permanent magnet or a wire carrying a current.

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11
Q

Describe the straight wire’s magnetic field

A

Concentric circles

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12
Q

What can a solenoid be used for?

A

Circuit breaker

Magnetic relay

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13
Q

What is the purpose of a relay?

A

Control high voltage system with low voltage or control high current system with low current

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14
Q

Describe the relay process

A

The low voltage circuit is on so there is a current in the solenoid. The magnetic field in the solenoid attracts the armature and the current flows through the contacts so the high voltage is on.

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15
Q

What is a circuit breaker?

A

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.

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16
Q

What increases the magnetic force?

A

Increasing current
Stronger magnet
Increasing length of wire in the field

17
Q

What are parts of an electrical motor

A

Coil of wire
Two magnets
Split ring commutator
Brushes

18
Q

How does the electrical motor work?

A
  1. The current flows in opposite directions on each side of the armature which will create two opposite forces act as different line making the armature only spin half a cycle
  2. The split-ring reverses the current direction through an armature every half turn so the armature will continue to spin in the same direction
19
Q

What increases the turning effect?

A

Increasing current
Increasing number of turns
Increasing area of the coil
Using a stronger magnet

20
Q

What happens when the coil is horizontal?

A

The turning effect will be maximum

21
Q

What happens as the turning effect as the coil rotates from horizontal to vertical?

A

It decreases

22
Q

What is faraday’s law?

A

The EMF induced in a conductor is proportional to the rate at which magnetic field lines are cut by the conductor

23
Q

What increases the induced EMF?

A

Moving wire faster
Stronger magnet
Increasing the length of wire inside the magnetic field

24
Q

What is a galvanometer?

A

A very sensitive ammeter

25
Q

What is Lenz’s Law?

A

An induced current always flows in the direction such opposes the change which produced it

26
Q

How can the size of the current be made bigger?

A

Magnet at a faster speed
Stronger magnet
More turns of wire on the coil

27
Q

What does an AC generator convert?

A

Mechanical work into electrical work

28
Q

How does an AC generator work?

A
  1. The wire cuts the m.f lines inducing an emf that causes induced current in the coils.
  2. If the wire is moved in the opposite direction the induced current also moves in the opposite direction
    This means that as a coil is rotated in magnetic field, the induced current reverses direction every half turn. This is called alternating current.
29
Q

How do I increase EMF in the AC generator?

A

Increase number of turns
Use a stronger magnet
Increase the area of the coil
Rotating the coil faster

30
Q

What are the types of transformers?

A

Step up transformer

Step down transformer

31
Q

What is a transformer made from?

A

Two coil and one on each side of a soft iron core

32
Q

Explain how the transformer can work

A

AC current passes through the primary core which creates a changing magnetic field in the iron core. The changing magnetic field then induces alternating current in the secondary coil. The induced emf depends on the number of coils in the secondary coils.

33
Q

Transformer equation

A

Voltage A/ Voltage B= Number of turns in A/ Number of turns in B

34
Q

Why do transformers only work with alternating current?

A

Using direct current will create a mf in the core but it will not be a changing mf and so no voltage will be induced in the second coil

35
Q

Power in the transformer

A

V1 * I1= V2 * I2

36
Q

Why does a transformer produce a very high voltage?

A

Minimise energy loss as current decreases therefore it is less expensive

IGCSE Physics (12 decks)

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