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Physics > 6 Magnetism and electromagnetism > Flashcards

6 Magnetism and electromagnetism Flashcards

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1
Q

What can magnets do?

A
  • Repel and attract eachother
  • Attract magnetic substances
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2
Q

Magnetic Materials

A

When placed in a magnetic field, becomes a magnet

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3
Q

Magnetic Elements

A
  • Iron
  • Cobalt
  • Nickel
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4
Q

What can materials containing a magnetic element be

A

Magnetic or non-magnetic

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5
Q

Properties of magnetically hard materials

A

Retain magnetism when removed from a magnetic field
* Difficult to magnetise and demagnetise

e.g. steel

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6
Q

Properties of magnetically soft materials

A

Lose magnetism when removed from a magnetic field

e.g. iron

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7
Q

Magnetic Field Line

A

Represent strength and direction of a magnetic field

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8
Q

Features of Magnetic Field Lines

A
  • Go from north to south
  • Never cross
  • Closer field lines = stronger field
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9
Q

Uniform Magnetic Field

A

Field lines are parallel and equally spaced apart
When opposite poles of 2 permanent magnets are put together

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10
Q

Null/neutral point

A

Where there is no magnetic field
When like poles of 2 permanent magnets are put together

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11
Q

What an electrical current in a conductor produce?

A

A magnetic field around it

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12
Q

Construction of electromagnets

A
  1. Wrap solenoid around a core
  2. For a strong electromagnet, core should be iron
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13
Q

What affects the strength of an electromagnet?

A
  • No. of turns
  • Current
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14
Q

What is a solenoid

A

A coil of wire

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15
Q

How to construct the field lines around a magnet

A
  • Sprinkle iron filings
  • Tap card to distribute iron filings
  • Use compass to show direction of lines
  • Mark where the compass points
  • Move compass to multiple places and along same line
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16
Q

Motor Effect

A

When a charged particle (e.g. electron) moves in a magnetic field, there is a force.
As long as its motion is not parallel to the field

17
Q

Factors that effect the motor effect

A
  • Greater current = greater strength of magnetic field = greater force
  • Reversing current or field direction = reverses direction of force
18
Q

How to predict the direction of the force in a magnetic field

A

Flemings Left Hand Rule
* Force
* Field
* Current

19
Q

Examples of when the motor effect is used

A
  • Electric Motor
  • Loudspeaker
20
Q

Motor Effect: Electric Motor

A
  • Made up of a cell which can rotate on a spindle.
  • Located within a magnetic field (magnets on either side)
21
Q

Motor Effect: Loudspeaker

A
  • An alternating current flows through a coil of wire (located between the poles of a magnet) producing a magnetic field
  • This interacts with the magnetic field of the permanent magnet
  • Puts a force on the coil (oscillates) and causes the speaker to oscillate = longitudinal sound wave
22
Q

Electromagnetic Induction

A

When a conductor cuts through a magnetic field, or a magnetic field changes through it = voltage is induced

23
Q

Experiment: Electromagnetic Induction

A

Move a bar magnet in and out of a coil of wire
Coil of wire is connected to an ammeter\

  • Moving magnet in and out of cell = alternating current
  • Moving it in and out quicker = bigger current
  • Pulling in and out = changes direction of current
24
Q

How to produce an alternating current

A

The conductor or the magnetic field must be moving

25
Q

Structure of a Transformer

A

2 coils linked by a core (made of a magnetic material)

26
Q

How can the size of the induced voltage be increased in a transformer?

A

Increase:
* Speed of rotation
* Strength of magnetic field
* Number of turns on coil
* Area of coil

27
Q

How a transformer works

A
  1. Primary/input coil acts as an electromagnet which produces a magnetic field
  2. This magnetic field induces a current in the secondary/output coil
28
Q

The National Grid Structure

A

Power Station
Step - up Transformer
National Grid (pylons)
Step - Down Transformer
Homes

29
Q

The National Grid

A
  1. To reduce power loss in transmission:
    * power loss is proportional to current squared
    * so high voltage is used
  2. Wires on pylons are very high voltage (400000V)
  3. Too high for homes, so step - down transformer is used.
30
Q

Direct Current

A

Current moves in a single direction

Physics (8 decks)

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