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IGCSE PHYSICS REVISION > Electricity and Magnetism Details > Flashcards

Electricity and Magnetism Details Flashcards

1
Q

Types of charge

A

-Positive(+) charge
-Negative(-) charge

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2
Q

Like charges…

A

repel

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3
Q

Unlike charges…

A

attract

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4
Q

The closer the charges…

A

the greater the force between them

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5
Q

Examples of good conductors

A

-Metals
-Carbon

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6
Q

Examples of poor conductors

A

-(Pure) water
-Earth

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7
Q

Examples of semi-conductors

A

-Silicon
-Germanium

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8
Q

Examples of insulators

A

-Plastics
-Glass
-Rubber
-Dry air

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9
Q

Relationship between charged and uncharged objects

A

A charged object will attract any uncharged object close to it

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10
Q

SI unit of charge

A

coulomb(C)

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11
Q

(referring to charge)Field lines always point…

A

from positive to negative charge

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12
Q

Where the electric field is strongest

A

Where the charges are most concentrated and the field lines are closest together(usually the sharpest curve of the conductor)

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13
Q

Conventional current direction

A

from positive to negative terminal

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14
Q

Direction of flow of electrons

A

from negative to positive terminal

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15
Q

SI unit of current

A

ampere(A)

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16
Q

SI unit of p.d.(potential difference)

A

volt(V)

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17
Q

If the p.d. across a cell is 2V, then…

A

2 joules of potential energy are given for each coulomb of charge

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18
Q

If charge flows at 3 coulombs per second, the current is…

A

3 amperes

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19
Q

Factors affecting resistance

A

-Length(proportional to resistance)
-Cross-sectional area(inversely proportional to resistance)
-Material

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20
Q

In metal conductors, resistance(in relation to temperature)…

A

increases with temperature

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21
Q

In semiconductors, resistance(in relation to temperature)…

A

decreases with temperature

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22
Q

There is a heating effect whenever current flows in a resistance(T/F)

A

True

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23
Q

SI unit for resistance

A

ohm(Ω)

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24
Q

Ohm’s law

A

the current is proportional to the p.d.(voltage)

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25
Q

Features of lamps connected in series

A

-The lamps share the same voltage from the battery(so each glows dimly)
-If one lamp is removed, the other one goes out too as the circuit is broken

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26
Q

Features of lamps connected in parallel

A

-Each lamp gets the full voltage from the battery as both are directly connected to it(so both glow brightly)
-If one lamp is removed, the other still keeps working as it is still part of an unbroken circuit

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27
Q

Features of resistors(or other components) in series

A

-The current in each of the components is the same
-The total p.d.(voltage) across all the components is the sum of the p.d.s across each of them

28
Q

Features of resistors(or other components) in parallel

A

-The p.d.(voltage) across each of the components is the same
-The total current in the main circuit is the sum of the currents in the branches

29
Q

(In terms of watts)1 kilowatt(kW) is…

A

1000 watts(W)

30
Q

(In terms of joules)1 kilowatt-hour(kWh) is…

A

3,600,000J

31
Q

Potential hazards of electricity

A

-Damaged insulation
-Overheating cables
-Damp conditions
-Excess current(from overloading of plugs, extension leads, single and multiple sockets)

32
Q

Function of a fuse

A

Overheats and melts if the current rises above a set amount, breaking the circuit in the process(and stops the current flowing)

33
Q

Two poles of a magnet

A

-North pole
-South pole

34
Q

Where the magnetic field is strongest

A

Where the fields are closest together

35
Q

In a magnet, the field lines run from…

A

north pole to south pole

36
Q

Ways to demagnetize a magnet

A

-Hammering the magnet
-Heating the magnet to a high temperature
-Pulling the magnet out of a solenoid through which an alternating current is passing

37
Q

Features of a magnetic field created by a current

A

-The magnetic field lines are circles
-The field is strongest close to the wire
-Increasing the current increases the strength of the field

38
Q

Right-hand grip rule(the one you use to find the field direction)

A

If you grip the wire with your right hand(so that your thumb points in the conventional current direction), your fingers will point in the same direction as the field lines

39
Q

Features of a magnetic field created by a current-carrying coil

A

There are magnetic poles at the ends of the coil

40
Q

Right-hand grip rule(the one used to find which way round the poles are in a current-carrying coil)

A

If you grip the coil with your right hand(so that your fingers point in the conventional current direction), your thumb will point towards the North pole of the coil

41
Q

How to make a permanent magnet

A

-Place a bar of a hard magnetic material into a solenoid
-Pass current through the solenoid(the hard magnetic material becomes magnetized)
-Even when the current is switched off it will stay magnetized

42
Q

Ways to increase the strength of the magnetic field of an electromagnet

A

-Increasing the current
-Increasing the number of turns of the coil

43
Q

Difference between an electromagnet and an ordinary magnet

A

An electromagnet can be switched on and off while an ordinary magnet cannot

44
Q

Type of magnetic materials that can be suitable as the core of an electromagnet

A

Soft magnetic materials

45
Q

Why hard magnetic materials cannot be the core of an electromagnet

A

They will stay magnetized(so they can’t be switched on or off)

46
Q

How to reverse the direction of the magnetic field in an electromagnet

A

Reverse the current

47
Q

Difference between a fuse and a circuit breaker

A

Circuit breakers can be reset(turned on again) after it has tripped(turned off)

48
Q

Ways to increase the force produced by a magnetic field

A

-Increasing the current
-Using a stronger magnet
-Increasing the length of the wire in the field

49
Q

Finger representations for Fleming’s left-hand rule

A

Thumb - Force
First finger(from thumb) - Field(N pole to S pole)
Second finger(from thumb) - Current(conventional current direction)

50
Q

Conditions for Fleming’s left-hand rule to apply

A

The current and field directions are at right angles

51
Q

Function of the commutator

A

Changes the direction of the current in the coil when the coil is nearly vertical(and the forces cannot turn it much further), allowing the forces to change direction and keep the coil turning

52
Q

Ways to increase the turning effect of the coil

A

-Increasing the current
-Using a stronger magnet
-Increasing the number of turns on the coil

53
Q

Ways to increase the induced electromotive force(and the current)

A

-Moving the coil faster
-Using a stronger magnet
-Increasing the length of wire in the magnetic field(eg. increasing the number of turns in the coil)

54
Q

Ways to reverse the induced electromotive force and the current

A

-Moving the wire in the opposite direction
-Turning the magnet round(so that the field direction is reversed)
-Pulling the magnet out of the coil

55
Q

Lenz’s law

A

The induced current always flows in a direction such that it opposes the change which produced it

56
Q

Finger representations for Fleming’s right-hand rule

A

Thumb - Motion
First finger(from thumb) - Field
Second finger(from thumb) - Current

57
Q

Situations when Fleming’s left-hand rule applies

A

When a current causes a motion

58
Q

Situations when Fleming’s right-hand rule applies

A

When a motion causes a current

59
Q

Ways to increase the maximum electromotive force(and the current)

A

-Increasing the number of turns in the coil
-Increasing the area of the coil
-Using a stronger magnet
-Rotating the coil faster

60
Q

Ways to increase the induced electromotive force at switch-on or switch-off un mutual induction

A

-The core of the electromagnet goes right through the second coil
-The number of turns on the second coil is increased

61
Q

Features of step-up transformers

A

-Have more turns on their output coil than their input coil
-Their output voltage is more than their input voltage

62
Q

Features of step-down transformers

A

-Have fewer turns on their output coil than their input coil
-Their output voltage is less than their input voltage

63
Q

Benefits of using alternating current over direct current for the mains

A

-Can be stepped up or down using transformers
-Can be generated more efficiently than direct current on a large scale

64
Q

Advantages of transmitting power at a high voltage over low voltage

A

-Less power is lost
-Less energy is wasted
-Thinner, lighter and cheaper cables can be used

65
Q

Resistance and length are…

A

directly proportional

66
Q

Resistance and cross-sectional area are…

A

inversely proportional

IGCSE PHYSICS REVISION (13 decks)

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