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PHYSICS > Magnetism and Electromagnetism > Flashcards

Magnetism and Electromagnetism Flashcards

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1
Q

What do all magnets have?

A

Two poles

North and South

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2
Q

What do magnetic field lines show?

A

the size and direction of magnetic fields

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3
Q

What is a magnetic field?

A

A region where magnetic materials experience a force

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4
Q

What direction do magnetic field lines point?

A

North to South

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5
Q

What kind of field will you find when you place the North and South poles of two permanent bar magnets near each other?

A

A uniform field

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6
Q

What two things can you use to investigate magnetic field patterns?

A

Compasses and Iron Fillings

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7
Q

A current-carrying wire creates a ….

A

magnetic field

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8
Q

The larger the electric current….

A

the stronger the magnetic field

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9
Q

What causes a wire to move?

A

When a current carrying wire is put between magnetic poles, the two magnetic fields affect one another. The result is a force on the wire.

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10
Q

Where does a wire have to be in proportion to the magnetic field?

A

at 90 degrees

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11
Q

What’s a good way of showing the direction of the force?

A

To apply current to a set of rails inside a horseshoe magnet.
A bar is placed on the rails which completes the circuit.
This generates a force that rolls the bar along the rails.

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12
Q

The stronger the magnetic field…

A

The stronger the force

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13
Q

What happens when you reverse the current or magnetic field?

A

The direction of the force also reverses

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14
Q

What can you do to remember the way which force acts?

A

Fleming’s Left-Hand Rule

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15
Q

Name 4 factors that will speed up an A.C electric motor

A

More current
More turns on the coil
Stronger magnetic field
A soft iron core in the coil

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16
Q

How can the direction of an A.C motor be reversed?

A

Swapping the polarity of the d.c supply

Swapping the magnetic poles over

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17
Q

How do loudspeakers work?

A

A.C electrical signals from an amplifier are fed to a coil of wire in the speaker which os wrapped around the base of a cone
The coil is surrounded by a permanent magnet so the a.c signals cause a force on the coil and make it move back and fourth
The movements make the cone vibrate and this creates sounds

18
Q

What is electromagnetic induction?

A

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

19
Q

What is the dynamo effect?

A

Using electromagnetic induction to transform kinetic energy into electrical energy

20
Q

Name the two ways you can get EM induction

A

When an electrical conductor moves through a magnetic field

When the magnetic field through an electrical conductor changes

21
Q

How can you test the dynamo effect?

A

By connecting an ammeter to a conductor and moving the conductor through a magnetic field
The ammeter will show the magnitude and direction of the induced current

22
Q

To get a bigger voltage in the dynamo effect you can…

A

INCREASE
strength of magnet
number of turns on the coil
speed of movement

23
Q

Like poles…

A

repel

24
Q

Opposite poles…

A

attract

25
Q

How does magnetic induction occur?

A

When a magnet is brought near a magnetic material, that material acts as a magnet.

26
Q

The closer the magnet and the magnetic material get…

A

The stronger the induced magnetism

27
Q

What is the magnetic field inside a current carrying solenoid like?

A

strong and uniform

28
Q

What is the magnetic field outside a current carrying solenoid like?

A

Like the one around a bar magnet.

29
Q

What is a solenoid magnet a type of?

A

electromagnet

30
Q

When is a magnetic material considered ‘soft’ ?

A

If it loses it’s induced magnetism quickly

31
Q

When is a magnetic material considered ‘hard’ ?

A

If it keeps it’s induced magnetism permanently

32
Q

Name an example of a soft magnetic material and a hard material.

A

Soft - Iron

Hard - Steel

33
Q

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

A

By adding a ‘soft’ iron core through the middle

34
Q

What do transformers do?

A

Change the size of the voltage of an alternating current

35
Q

What do transformers have?

A

Two coils, the primary and secondary, joined with an iron core.

36
Q

What happens when an alternating voltage is applied across the primary coil of a transformer?

A

The magnetically soft iron core magnetises and demagnetises quickly, inducing an alternating voltage in the secondary coil.

37
Q

In a transformer, the ratio between the primary and secondary voltages is the same as…

A

The ratio between the number of turns on the primary and secondary coils

38
Q

What do step-up transformers do?

A

Step the voltage up. They have more coils on the secondary coil than on the primary coil/

39
Q

What do step-down transformers do?

A

Step the voltage down. They have more turns on the primary coil than in the secondary.

40
Q

What is the transformer equation?

A

Input (primary) Voltage / Output (secondary) Voltage = No. of turns on primary / No. of turns on secondary

41
Q

Another way of saying input power = output power

A

VpIp = VsIs

42
Q

How do transformers work when transmitting electricity across the country?

A
  • The voltage produced by power stations is too low to be transmitted efficiently, so a step-up transformer is used to boost the voltage before it is transmitted
  • Step-down transformers are used at the end of the journey to reduce the voltage so it’s more useful and safer to use

PHYSICS (8 decks)

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