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GCSE Edexcel Separate Physics > SP12 Magnetism and the Motor Effect > Flashcards

SP12 Magnetism and the Motor Effect Flashcards

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1
Q

Describe the law of magnetism

A
  • Two like poles (e.g.: S,S or N,N) will repel each other
  • Two unlike poles will attract each other
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2
Q

What type of force is the attraction and repulsion of different magnetic poles?

A

Non contact force

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3
Q

What elements are magnetic?

A
  • Iron
  • Nickel
  • Cobalt
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4
Q

How do we test if an unknown material is a magnetic metal or a magnet?

A
  • If it can be repelled by the magnet, the material itself is a magnetic
  • If it can only be attracted by the magnet, the material is a magnetic metal
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5
Q

What are the two types of magnets?

A
  • Permanent
  • Induced
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6
Q

Define permanent magnet

A

A material that will produce its own magnetic field. It will not lose its magnetism

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7
Q

Define induced magnet

A

When a magnetic material is placed into a magnetic field, it can temporarily turn into a magnet

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8
Q

How can we induce a magnet?

A

By stroking it with a permanent magnet.

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9
Q

Why does stroking the magnetic material with a magnet induce its magnetism?

A

It aligns all the domains of the material in the same direction, creating a temporary magnet

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10
Q

Define magnetic field?

A

The region around a magnet where a force acts on another magnet or on a magnetic material

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11
Q

What are magnetic field lines used for?

A

Used to represent the strength and direction of a magnetic field

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12
Q

How do magnetic field lines travel?

A

Point from North to South

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13
Q

How is the strength of the magnetic field shown?

A

Spacing of the magnetic field lines:
- close together = strong magnetic field
- far apart = weaker magnetic field

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14
Q

What is a uniform magnetic field?

A

One that has the same strength and direction at all points

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15
Q

How is a uniform magnetic field shown?

A
  • equal spacing between all the magnetic field lines
  • arrow going from north to south
  • produced between the gaps of two opposite poles
  • the field will not be uniform outside that point
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16
Q

Where is the magnetic field of a bar magnet the strongest?

A

At the poles

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17
Q

Why does the magnetic field become weaker as we move away from the bar magnet?

A

The magnetic field lines are getting further apart, so it cannot attract or repel as much

18
Q

How do we know that the Earth’s core is magnetic?

A

A free suspended magnetic compass will align itself with Earth’s field lines and always point North

19
Q

Why is Earth’s magnetic north actually its geographic south pole?

A
  • a compass is basically a suspended bar magnet
  • its north pole lines up with that of the Earth’s geographic north pole
  • which by the law of magnetic attraction cannot be right
  • therefore, the north of the compass must be lining up with the Earth’s magnetic south
20
Q

What happens when a current flows through a wire?

A

A magnetic field is produced

21
Q

Describe how to find the direction of the magnetic field using the right hand rule

A
  • Thumb: points along the direction of the current
  • Magnetic field has a direction similar to the way your fingers are pointing
22
Q

How do we change the direction of the magnetic field using current?

A

reversing current = reversing direction of the magnetic field

23
Q

How do we increase the strength of a magnetic field produced due to a current?

A
  • Increase the size of the current
  • wrapping the wire in coils also increases the size of the current
24
Q

What does the strength of the magnetic field depend on?

A
  • size of the current
  • distance from the long straight conductor
25
Q

What is a solenoid?

A

A series of coils that has a similar magnetic field as a bar magnet

26
Q

Describe the magnetic field of a solenoid

A
  • uniform
  • similar to that of a bar magnet
27
Q

Why is the magnetic field of a solenoid uniform?

A

Coiling the wire causes the field to align

28
Q

How can we work out the poles of a solenoid?

A
  • needs to be viewed from the end
  • if the current is travelling in a clockwise direction, then it is the south pole
  • if the current is travelling in an anticlockwise direction, then it is the north pole
29
Q

How do we increase the magnetic field of a solenoid?

A
  • increase the current
  • increase the number of coils
  • adding an iron core
30
Q

When does the motor effect occur?

A

When a wire with current flowing through it is placed in a magnetic field and experiences a force

31
Q

What is the effect of a motor effect?

A

The interaction of two magnetic fields:
- one is produced around the wire due to current flowing through it
- second is the magnetic field where the wire is placed between

This produces a force

32
Q

How must the wire be placed in relation to the magnetic field for a motor effect to be produced?

A

Perpendicular to each other

33
Q

What does the size of the force of a motor effect depend on?

A
  • strength of magnetic field
  • strength of current in wire
  • length of wire
34
Q

How can we increase the size of the force in a motor effect?

A
  • increasing the amount of current that flows through a wire
  • using stronger magnets
35
Q

Describe the magnetic field around a wire

A

Circular

36
Q

Describe Flemmings Left hand rule

A
  • thumb: represents force
  • first finger: represents magnetic field
  • middle finger: represents current
37
Q

What is Flemming’s left hand rule used to find out?

A

The direction of the force/current/magnetic field in a motor effect

38
Q

What is the equation used to calculate force in a motor effect?

A

Force = Magnetic flux density (field strength) x current x length of wire

39
Q

What can the motor effect be used for?

A

Force produced by the magnetic field and current is used to cause rotation, therefore producing a D.C. motor

40
Q

How does motor effect cause movement?

A
  • The current will flow in opposite directions on each side of the coil
  • force produced from the magnetic field will push one side of the coil up and the other side down
  • causing the coil to rotate
41
Q

What is the split ring commutator used for?

A

Reverses the direction of the current flow

GCSE Edexcel Separate Physics (18 decks)

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