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Physics > Magnetism and Electromagnetism > Flashcards

Magnetism and Electromagnetism Flashcards

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1
Q

At which part of a magnet are the magnetic forces strongest?

A

the poles of the magnet

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2
Q

What happens when 2 magnets are brought close to each other?

A

they exert a force on each other

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3
Q

What type of force is exerted if 2 like poles of a magnet are brought near each other?

A

a repulsive, non-contact force

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4
Q

What type of force is exerted if 2 unlike poles of a magnet are brought near each other?

A

an attractive, non-contact force

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5
Q

What is the difference between a permanent magnet and an induced magnet?

A
  • permanent produces its own magnetic field
  • induced becomes magnetic when placed in a magnetic field
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6
Q

What type of force does induced magnetism always cause?

A

a force of attraction

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7
Q

What happens when an induced magnet is removed from a magnetic fied?

A

induced magnet loses most/all of its magnetism

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8
Q

What is a magnetic field?

A

region surrounding a magnet where another magnet or magnetic material experiences a non-contact force

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9
Q

Give 4 examples of magnetic materials

A
  • iron
  • steel
  • cobalt
  • nickel
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10
Q

What can always be said about the force between a magnet and magnetic material?

A

it is always attractive

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11
Q

How does the strength of a magnetic field alter as you move further away from the magnet producing it?

A

the magnetic field strength decreases the further you move away

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12
Q

In what direction does a magnetic field point?

A
  • in the direction that a north pole would experience a force if placed in the field
  • from north seeking pole to south seeking pole of a magnet
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13
Q

What does a magnetic compass contain?

A

a small bar magnet that points in the direction of the Earth’s magnetic field

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14
Q

What is produced when current flows through a conducting wire?

A

a magnetic field is produced around the wire

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15
Q

What determines the strength of the magnetic field around a current-carrying wire?

A
  • magnitude of the current flowing through the wire
  • distance from the wire
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16
Q

What is a solenoid?

A

a coil of wire which when current passes through creates a strong magnetic field

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17
Q

Describe the magnetic field found inside a solenoid

A

strong and uniform

18
Q

What is an electromagnet?

A
  • a solenoid with an added iron core
  • adding the iron core increases the strength of the magnetic field
19
Q

What is the motor effect?

A

when a force is exerted between a magnetic field and a current-carrying conductor placed in that field

20
Q

What rule is used to determine the force experienced due to the motor effect?

A

Fleming’s Left-Hand Rule

21
Q

When using Fleming’s left hand rule what does the forefinger represent?

A

direction of the magnetic field

22
Q

When using Fleming’s left hand rule what does the second finger represent?

A

direction of current flow in the conductor

23
Q

What factors affect the size of the force on a current-carrying wire in a magnetic field?

A
  • magnitude of the current flowing through the conductor
  • strength of the magnetic field that the conductor is placed in
24
Q

If the direction of current in a current-carrying wire placed in a uniform magnetic field is reversed, what happens to the force?

A

the direction of the force is reversed

25
Q

If the strength of the current in a current-carrying wire placed in a uniform magnetic field is increased, what happens to the force?

A

the strength of the force is increased

26
Q

What criteria must be met for the equation linking force, magnetic flux density, current and length to hold?

A

conductor must be at right-angles to the magnetic field it is placed in

27
Q

What is the unit used for magnetic flux density?

A

Tesla, T

28
Q

How does an electric motor work?

A
  • a coil of wire, carrying a current, is placed in a magnetic field
  • the forces on the two sides perpendicular to the field experiences forces in opposite directions
  • this causes a rotational effect
29
Q

How do loudspeakers make use of the motor effect?

A

the motor effect is used to convert variations in the current of an electrical circuit into the pressure variations which produce audible sound

30
Q

Explain how a loudspeaker works

A
  • a cone with a wire wrapped around it is connected to an a.c power supply and is placed in a permanent magnetic field
  • when current flows through the wire, it creates a second magnetic field, which interacts with the permanent field
  • this produces a force which causes the cone to vibrate
31
Q

How is the pitch of the sound from a loudspeaker changed?

A
  • frequency of the a.c current is altered
  • this creates a different frequency of vibration in the cone
32
Q

What happens when an electrical conductor moves relative to a magnetic field?

A

a potential difference is induced across the ends of the conductor

33
Q

What happens to an electrical conductor when there is a change to the magnetic field that it is placed in?

A

a potential difference is induced across the ends off the conductor

34
Q

What is the requirement for an induced potential difference to cause a current flow?

A

the conductor must form a closed loop or be part of a complete circuit

35
Q

What can be said about the direction of the magnetic field produced by an induced current?

A
  • the direction of the field is such that it opposes the change that induced the current
  • this change is either the movement of the conductor or a change to the field
36
Q

What are 2 ways that the generator effect is used to generate different types of current?

A
  • in an alternator to produce alternating-current
  • in a dynamo to produce direct-current
37
Q

What electromagnetic effect does a microphone take advantage of and how?

A
  • the generator effect
  • it converts the pressure variations in sound waves into alternating current in a circuit
38
Q

Describe the makeup of a basic transformer

A

a primary coil and a secondary coil or wire wrapped around an iron core

39
Q

Why is iron used as the core for a transformer?

A

it is easily magnetised

40
Q

Explain how a transformer works

A
  • an alternating current flows through the primary coil
  • this induces a changing magnetic field in the core
  • this changing magnetic induces a current to flow in the secondary coil
41
Q

Why must the current flowing through the primary coil of a transformer be alternating?

A
  • for current to be induced in the secondary coil, the magnetic field in the core must be continuously changing
  • for the magnetic field to be changing, the current in the primary coil must be alternating
42
Q

What can be said about the electrical power input and output of a 100% efficient transformer?

A

the electrical power input is equal to the electrical power output

Physics (8 decks)

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