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Physics > Unit 12 & 13 - Magnetism And The Motor Effect/ Electromagnetic Induction > Flashcards

Unit 12 & 13 - Magnetism And The Motor Effect/ Electromagnetic Induction Flashcards

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1
Q

What is a permanent magnet?

A

Something that is always magnetic

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2
Q

What materials do magnets attract?

A

Magnetic materials

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3
Q

Give 4 magnetic materials

A

Iron, steel, nickel and cobalt

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4
Q

What is a magnetic field?

A

The space around a magnet where it affects other magnetic objects

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5
Q

What are the full names for the ends of a magnet

A

North-seeking pole

South-seeking pole

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6
Q

What is an induced magnet

A

When a magnetic material is in a magnetic field and becomes a magnet itself, it is no longer a magnet when it leaves the magnetic field

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7
Q

Give 3 examples of how magnets are used

A

Electric motors, loudspeakers, knife holders

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8
Q

What is used to find the shape of a magnetic field

A

Plotting compasses

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9
Q

How do you use a plotting compass

A

Place near a magnet, mark the direction, use this point to line up next mark

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10
Q

What type of magnetic field do 2 magnets form

A

A uniform magnetic field

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11
Q

What is the earths magnetic field caused by

A

Electric currents in the molten outer core, nickel and iron

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12
Q

What depends on the magnetic effect of electrical currents?

A

Electric motors

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13
Q

What does the direction of the magnetic field depend on

A

Direction of current

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14
Q

What rule is used for direction of magnetic field

A

Right thumb rule

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15
Q

What does the strength of a magnetic field depend on

A

The size of the current

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16
Q

What is a solenoid

A

When a wire is made into a coil

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17
Q

What is the magnetic field shape of a solenoid

A

Uniform in the center and opposite directions outside

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18
Q

What is an electromagnet?

A

A could of wire with a current flowing though it

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19
Q

What cans strengthen the magnetic field of an electromagnet

A

Putting a piece of iron inside it

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20
Q

What is the motor effect

A

When a force is produced as a result of a current carrying wire being between 2 magnets

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21
Q

What happens in the motor effect

A

The current in the wire creates a magnetic field around the wire which interacts with the magnetic field between the magnets

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22
Q

When is the force from the motor effect the strongest?

A

When the wire is at right angles to the magnetic field

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23
Q

What rule shows the direction f the force from the motor effect

A

Fleming’s left hand rule

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24
Q

What does each finger represent in the left hand rule

A

F - force
B - magnetic field
I - current

25
Q

What 3 factors does the size of the force from the motor effect depend on

A

Magnetic field strength
Current size
Length of the wire

26
Q

What is the strength of the magnetic field measured in?

A

Newton’s per amp metre (N/A m)

Tesla (T)

27
Q

What is the equation to calculate the force from the motor effect

A

F = B x I x L

28
Q

What is the role of a split ring commutator on an electric motor

A

To switch the direction of the current (each half is connected to an end of the coiled wire, as it turns, it constantly brushed past the + and - end of the circuit)

29
Q

How is a p.d induced on a wire

A

When a wire is moving into a magnetic field, however, if the wire stops moving (even in the magnetic field) there is no p.d

30
Q

What is caused as a result of a p.d being induced

A

A current

31
Q

Why are wires coiled in a magnetic field

A

So there is more current in the magnetic field so there is more current created

32
Q

What 3 factors affect the amount of p.d induced?

A

The number of coils, strength of the magnetic field, how fast the magnetic field changes of moved past the coil

33
Q

Besides a change in magnetic field, what can also induce a p.d

A

Is a wire is moved into a magnetic field

34
Q

How does reversing the direction of the movement of the magnetic field affect the direction of the p.d

A

It reverses the direction also

35
Q

What direction does a current flow

A

Out negative, in positive

36
Q

What direction does a magnetic field travel in

A

Out N in S

37
Q

What happens when a magnet is moving in and out of a coil of wire

A

A current is induced on the wire which creates it own magnetic field

38
Q

On a coil of wire that has a current induced, what makes one end of the wire N

A

If the N end of a magnet is moving into the coil

39
Q

What is the generator effect

A

When a conducting wire is moved into a magnetic field, a p.d is induced, if the wire is complete, a current is also created

40
Q

How does the generator effect produce an alternating current?

A

Since the edges of the coil are continuously switching direction, up the down, the direction of p.d is also switching. The p.d is 0 every time the coil is parallel to the magnetic field

41
Q

Why in an alternator are the ends of the wire connected to 2 different slip rings

A

To allow the current to pass out of the coil and change direction

42
Q

What are generators used in

A

Power stations

43
Q

What is a dynamo

A

A generator with a commutator

44
Q

How does a commutator work in a generator

A

The ends of the coil are connected to each half so when it spins, the direction of the current changes, causing it to always stay positive

45
Q

What do microphones do

A

They convert the pressure variations in sound waves into variations in current in electrical circuits

46
Q

How do microphones work

A

Sound waves cause variations in pressure, this makes a diaphragm vibrate, the diaphragm moves a coil of wire backwards and forwards which has a magnet inside it (a current is induced as a magnet moves in a wire)

47
Q

What is the national grid

A

A system of wires an cables that sends electricity to homes and schools from power stations

48
Q

Along the national grid, when is there the most energy wasted

A

Along the transmission lines

49
Q

What happens if the p.d is increased along the national grid

A

The current decreases

50
Q

Why are transformers used?

A

To change the p.d and current so less energy is wasted by heating

51
Q

What is a step-up transformer

A

A transformer that increases the voltage and decreases the current

52
Q

What is a transformer made of

A

2 coils of insulated wire wound into an iron core, no electrical connection between the coils

53
Q

What type of a current do transformers use

A

Alternating current

54
Q

How does a transformer work

A

Since there is a current supplied to the primary coil, a magnetic field is produced. The current alternates in direction so the magnetic field does also. The magnetic field is transmitted along the iron core and to the secondary coil. Since the mf is changing, a p.d is induced, causing a current to flow out the other end

55
Q

How does a step-up transformer work

A

There are more coils in the secondary coil than the first so when the p.d is induced, it is greater at the secondary coil, causing the current to decrease

56
Q

Why do transformers only work with ac

A

The current must change direction in order for a p.d to be induced

57
Q

What is the equation to work out the p.d in a transformer

A

PC p.d/ SC p.d = PC number of turns/ SC number of turns

58
Q

What is charge measured in

A

Coulombs

59
Q

What are the 3 equations for power

A 
P = I x V
P = E/ t
P = I^2 x R

Physics (12 decks)

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