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CGP Physics > Section 6 - Magnetism and Electromagnetism P1 > Flashcards

Section 6 - Magnetism and Electromagnetism P1 Flashcards

1
Q

What two poles do all magnets have?

A

A north and south

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2
Q

Define magnetic field:

A

It’s a region where magnetic materials experience a force

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3
Q

What are the metals that are magnetic materials?

A
  • iron
  • steel
  • nickel
  • cobalt
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4
Q

What are magnetic field lines used to show?

A

Show the size and direction of magnetic fields

-ALWAYS POINT FROM NORTH TO SOUTH

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5
Q

What does placing the north and south poles of two bar magnets near each other create?

A

-creates a uniform field between the two magnets

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6
Q

Describe a practical for how magnetic field lines can be seen using compasses:

A
  • compasses and iron fillings align themselves with magnetic fields
  • can use multiple compasses to see the field lines coming out of two bar magnets
  • could use iron fillings on a piece of paper with a magnet below and you can see the field lines
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7
Q

What do magnets affect?

A

Magnetic materials and other magnets

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8
Q

What do like poles do, and what do opposite poles do?

A

Like poles - repel

Opposite poles - attract

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9
Q

What are magnetic materials attracted to?

A

Both poles attract magnetic materials

  • the material acts like a magnet when it is brought near to a magnet
  • the magnetism has been induced by the original magnet
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10
Q

What affects induced magnetism?

A

distance

-the closer the magnet and magnetic material get the stronger the induced magnetism will be

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11
Q

What does an electric current in a conductor produce?

A

A magnetic field around it

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12
Q

What affects a magnetic field around an electric current flowing through a wire?

A
  • larger current, stronger magnetic field

- direction of current, determines direction of magnetic field

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13
Q

What are the two ways magnetic materials can be described?

A

soft - if it looses its magnetism quickly

hard - if it keeps its magnetism permanently

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14
Q

What is an example of a soft magnetic material?

A

iron

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15
Q

What is an example of a hard magnetic material?

A

steel

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16
Q

What material is used in transformers?

A

iron - because for mains electricity it needs to be magnetised and demagnetised 50 times er second

17
Q

How can you increase the strength of a magnetic field around a solenoid?

A

By adding a soft iron core

18
Q

When a current-carrying wire is put between magnetic poles, what happens?

A

-the two magnetic fields affect one another
-the result is a force on the wire
-this causes the wire to move
THIS CALLED THE MOTOR EFFECT

19
Q

What angle does a wire have to be at within two magnetic poles to experience the full force?

A

90° to the magnetic field will experience full force

  • parallel won’t experience any force
  • angles in between will feel some force
20
Q

What factors determine the way that the force will affect the wire between two poles?

A
  • the magnetic field of the magnets

- the direction of current in the wire

21
Q

What factors increase the magnitude of the force that the wire will get when a current is flowing through it when it’s between two poles?

A
  • increasing the strength of the magnetic field

- increasing the amount of current flowing through the conductor

22
Q

What can you do to determine the direction at which the force acts from the motor effect?

A

Fleming’s left hand rule

  • use your left hand
  • point your first finger in the direction of the field
  • point your second field in the direction of the current
  • point your thumb in the direction of the force (motion)
23
Q

What direction does a magnetic field go?

A

From north to south

24
Q

What direction does current go?

A

From positive to negative

25
Q

What factors speed up a DC electric motor?

A
  • more current
  • more turns of the coil
  • stronger magnetic field
  • a soft iron core in the centre
26
Q

How does a DC electric motor work?

A
  • a coil of wire is placed between a north and south pole
  • the forces act one up and the other down, it rotates
  • the split-ring commutator keeps the motor rotating in the same direction
27
Q

What does a split-ring commutator do?

A

It swaps the contacts every half turn to keep the motor rotating in the same direction

28
Q

How can the direction of a DC motor be changed?

A
  • swapping the polarity of the DC supply

- swapping the magnetic poles over

29
Q

How do loudspeakers work?

A

AC electric signals from an amplifier are fed to a coil of wire in the speaker, which is wrapped around the base of a cone

  • the coil is surrounded by a permanent magnet
  • this causes the coil to move back and forth
  • the movements cause the cone to vibrate which creates sound
30
Q

Define electromagnetic induction:

A

The creation of a voltage (and maybe a current) in a wire which is experiencing a change in magnetic field.

31
Q

What is the dynamo effect?

A

Using electromagnetic induction to generate electricity using energy from kinetic energy stores is called the dynamo effect. (in a power station, this energy is provided by the turbine)

32
Q

What two situations do you get electromagnetic induction?

A
  • when an electrical conductor moves through a magnetic field
  • when the magnetic field goes through an electrical conductor changes
33
Q

How can you test the dynamo effect?

A

You can test the dynamo effect by connecting an ammeter to a conductor and moving the conductor through a magnetic field (or a magnet through the conductor)
-the ammeter will show the magnitude and direction of the induced current

34
Q

How can you get a bigger voltage from the dynamo effect?

A

increasing. ..
- the strength of the magnet
- the number of turns of the coil
- the speed of the movement

35
Q

How do AC generators work?

A
  • generators rotate a coil in a magnetic field
  • as the coil spins, a current is induced by the coil, this current changes direction every half turn
  • AC generators have slip rings and brushed so the contacts don’t change every turn
  • this results in the production of AC voltage
36
Q

What type of electricity do power stations generate?

A

AC because they use AC generators

-they just get the energy needed to turn the coil or magnetic field in different ways

CGP Physics (16 decks)

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