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Physics IGCSE > 6 - magnetism and electromagnetism > Flashcards

6 - magnetism and electromagnetism Flashcards

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1
Q

What are ampere, volts, and watts for?

A

Ampere (A), the measure of electric current
Volt (V), the measure of voltage
Watt (W), the measure of power

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2
Q

What happens when you have a north pole and south pole of 2 magnets facing each other?

A

They attract - because opposites attract

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3
Q

What will happen when you have two magnets and you face their north pole together?

A

They will repel because like charges repel

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4
Q

what are the properties of magnetically hard materials?

A
  • Permanent magnets made from steel.
  • Retains magnetism once magnetized.
  • such as iron, cobalt and nickel (steel contains iron)
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5
Q

what are the properties of magnetically soft materials?

A
  • Temporary magnets made from Iron.
  • Lose magnetism easily.
  • suitable for temporary magnets
  • such as iron, coblat and Nickle (steel contains iron)
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6
Q

What do the magnetic field lines show?

A

The volume of space where magnetism can be detected.
- Also the shape, strength and direction of a magnetic field

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7
Q

Where are the field lines drawn from?

A

North to south

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8
Q

How can you determine the strength of a magnetic field?

A

The distance between the field lines

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9
Q

What is electromagnetism?

A

When current flows through a wire, a magnetic field is created around the wire (no current no field)

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10
Q

What are the 4 magnet rules?

A

MAGNETIC RULE #1:
Magnets have poles
- North
- South

MAGNETIC RULE #2:
When you break a magnet it will still have to poles and it wont be weaker

MAGNETIC RULE #3:
Magnets have pole
- SAME poles REPEL
- OPPOSITE poles ATTRACT

MAGNETIC RULE #4:
Magnetic material will be attracted by a magnet but only magnets will repel

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11
Q

What are some Magnetic substances that attract?

A
  • Iron
  • Nickel
  • Cobalt
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12
Q

why do some materials that are not magnetic become magnetic once placed in a magnetic field?

A

This is because the magnetic field causes electrons to align and form poles. This happens in steel, cobalt, and nickel.

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13
Q

What is Fleming’s right-hand rule?

A

The thumb points in the direction of the current
other fingers show the direction of the magnetic field

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14
Q

How can the strength of the field around a current be increased?

A
  1. Increasing the current.
  2. Wrapping wire into a coil or solenoid
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15
Q

What happens when magnetic materials are brought near or touching a pole of a strong/ permanent magnet?

A

They become magnets. This magnetic character is induced in the objects and it is removed when the permanent magnet is removed. This is a temporary magnet

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16
Q

explain the practical to investigate the magnetic field pattern for a permanent bar magnet or two magnets: (compass)

A
  1. Place your bar magnet in the centre of the next page and draw around it.
  2. Place a compass at one pole of the bar magnet.
  3. Draw a ‘dot’ to show where the compass is pointing,
  4. Move the compass so the opposite end of the needle is pointing to the dot,
  5. Repeat steps 3 and 4 until to reach the other pole of the magnet.
  6. Do this procedure at least 5 times from different points on the pole of the magnet.
  7. Join up your dots to create the field line plots
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17
Q

explain the practical to investigate the magnetic field pattern for a permanent bar magnet or two magnets: (iron fillings)

A
  1. Place a sheet of paper over a bar magnet.
  2. Sprinkle a thin layer of Iron filings over the paper and then tap the paper gently.
  3. The iron filings point themselves along the lines of flux.
  4. Lines of flux always point to the South and away from North
  5. To prove, the shape and direction of lines of flux in a magnetic field can be proved using compasses.
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18
Q

What is a uniform magnetic field?

A

A uniform magnetic field is comprised of straight, parallel lines which are evenly spaced. Between two opposite charges on flat magnets, a uniform magnetic field is formed.

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19
Q

What happens if there is an electrical current in a conductor? What is a conductor?

A

If an electric current is in a conductor (object/material that allows electricity to flow), it produces a magnetic field around it.

20
Q

What is the motor effect?

A

If there’s a wire with a current running through between two magnetic poles, a force will push the wire up or down.

21
Q

How can you determine the direction of a force when you put a current-carrying wire into a magnetic field?

A
  • Direction of the field
  • Direction of the current
  • Use Flemings left hand rule
22
Q

What is full force?

A

Full force: when the wire is 90 degrees to the magnetic field.

23
Q

What happens if the wire is parallel to the field lines

A

If the wire runs along the magnetic field, there won’t be any force.

24
Q

What happens to the force when the strength of the magnetic field increases?

A

As the strength of the magnetic field increases, so will the strength of the force

25
Q

What happens to the force when the size of the current passing through the conductor increase?

A

The larger the current (passing through conductor) increases, so will the force

26
Q

Explain how a simple DC motor works:

A
  • Current flows in the wire/coil.
  • This creates a magnetic field around the wire/coil.
  • This magnetic field interacts with the field from the permanent magnet.
  • This produces a force on the wire/coil which moves the wire/coil.
  • The split-ring commutator changes the direction of the current every half turn as it spins.
  • This reverses the direction of the forces, allowing -the coil to continue spinning.
27
Q

How can you increase the speed in a DC motor?

A
  • Add more turns to the coil
  • use a soft iron core (in the coil)
  • Use a stronger magnetic field
  • Use more current
28
Q

Explain how a Loudspeaker works:

A
  • An alternating current from the source passes through the coils in the speaker.
  • This current is constantly changing direction and magnitude
  • This current creates a magnetic field around the coil
  • This field interacts with the magnetic field from the permanent magnets
  • Creating a constantly changing force on the coil.
  • This causes the coil to vibrate in and out as the direction of the force changes, moving the cone
  • The cone causes vibrations which we hear as sound waves.
29
Q

What does Fleming’s left-hand rule tell you?

A

Tells you which way the force is acting.
Thumb: force

First finger: Magnetic Field

Second finger: Current

30
Q

What are the rules to show the direction of a magnetic field around a current-carrying wire?

A

X - into the page
O - comes out of the page

31
Q

What are the 2D rules to show the direction of the current?

A

Circle with an X - away from you
Circle with a dot - towards you

32
Q

how do you know the direction of the current if it shows you a circuit instead of arrows?

A

The longer part of the cell is the positive electrons and they travel from + to -

33
Q

Factors that increase the force of the wire (during the motor effect):

A
  • Increase the current flowing through
  • Use a stronger magnetic field
34
Q

What is electromagnetic induction?

A

Process of using a magnetic field to produce a voltage, and if it’s in a closed circuit, a current. (bring about a magnet by moving electrons)

35
Q

What happens if the wire is perpendicular to the magnetic field?

A

If wire is moved 90 degrees to the magnetic field= largest voltage/current produced

36
Q

What happens if the wire is parallel to the magnetic field?

A

If wire is moved parallel to the magnetic field= no voltage/current produced

37
Q

How is a voltage induced using a magnet and a coil?

A
  • use a current-carrying wire
  • get a magnet and move it through the coil
  • the field lines cut electrons in the coil inducing a voltage
38
Q

Factors affecting the strength of the voltage/current:

A
  • Strength of the magnetic field
  • The speed of the wire
  • Number of turns around the wire
39
Q

What is emf?

A

electro motive force

40
Q

How can electricity be generated using a magnet and coil?

A

Electricity can be generated by either moving a magnet inside a coil of wire or rotating a coil inside a permanent magnetic field.

41
Q

Give the model answer for explaining a generator (Rotating coil):

A

Model answer for a generator (Rotating coil):
· Coil is rotated within a magnetic field
· As it turns the coil cuts the magnetic field lines.
· This induces a voltage (or current) in the coil.
· This can then be connected to an existing circuit.
· In a generator, energy is converted from kinetic (mechanical) energy into electrical energy.
· The size of the induced voltage (or current) can be increased by:
· Using a stronger magnet
· Having more turns in the coil
· Spinning/moving the coil faster.

42
Q

Give th model answer for explaining a generator (Rotating magnet)

A

Model answer for a generator (Rotating magnet)
· Magnet is rotated within a coil
· As it turns the coil cuts the constantly changing magnetic field lines from the magnet.
· This induces a voltage (or current) in the coil.
· This can then be connected to an existing circuit.
· In a generator, energy is being converted from kinetic (mechanical) energy into electrical energy.
· The size of the induced voltage (or current) can be increased by:
· Using a stronger magnet
· Having more turns in the coil
· Spinning/moving the magnet faster.

43
Q

What happens when the North pole of a magnet moves into the coil?

A

The induced current flows in such a direction, to produce a North pole to oppose the approaching magnet.

44
Q

What happens when the magnet’s South pole is leaving the coil?

A

The induced current flows in such a direction, to produce a North pole to oppose the leaving magnet.

45
Q

how do you make the coil a magnet?

A

We make the coil a magnet by moving electrons in the coil. Whatever the magnet does, the coil doesn’t want that.

46
Q

What pole is created when the current moves anti-clockwise?

A

North pole (aNti)

47
Q

What pole is created when the current moves clockwise?

A

South pole

Physics IGCSE (9 decks)

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