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Physics GCSE > Topic 9 - Electricty & Circuits and Static Electricity > Flashcards

Topic 9 - Electricty & Circuits and Static Electricity Flashcards

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1
Q

voltage/potential difference

A

the pressure used to push the free electrons around the circuits
-> amount of potential energy the cell transfers to each coulomb of charge flowing through it

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2
Q

which way does the conventional current direction go

A

goes from the positive terminal to the negative terminal of the battery

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3
Q

series circuit

A

only one route

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4
Q

parallel circuit

A

circuit that contains different junctions (branches) for the current take different routes

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5
Q

unit for electric current

A

amps (A)

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6
Q

ammeter

A

measures the current passing through a component or circuit

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7
Q

what is a source of potential difference

A

cell or battery

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8
Q

what happens to the current if the potential difference is increased

A

the current increases

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9
Q

unit for potential difference

A

volts

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10
Q

voltmeter

A

measures the voltage

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11
Q

where is a voltmeter connected?

A

a voltmeter is always connected in parallel to measure the potential difference across the component or circuit

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12
Q

what is the unit for electric charge

A

coulombs (C)

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13
Q

current

A

rate a which electrons flow past a point in an electrical circuit

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14
Q

what is the current in a metal

A

flow of electrons

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15
Q

size of the current at any point

A

tells you how much charge flows last that point each second

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16
Q

electrical current

A

The rate of flow of charge

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17
Q

charge equation

A

charge = current x time

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18
Q

potential energy

A

The energy stored in the circuits electrons due to their position in the electric field

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19
Q

how do you get energy to a circuit

A

The cell transfers energy to the charge so the charge then has a potential to transfer energy to other components in the circuit

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20
Q

Energy transferred equations

A
  • Energy transferred = charge move x potential difference
  • Energy transferred = current x potential difference x time
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21
Q

units for resistance

A

ohms

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22
Q

potential difference equation

A

Potential difference = current x resistance

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23
Q

Why is there a greater potential difference across some resistors but not others?

A

because resistors with higher resistance have greater potential difference

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24
Q

what happens in a parallel circuit when resistors are added?

A

The total resistance of the circuit is less than the resistance of the individual resistors because there are now more paths for the current

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25
Q

resistance

A

how hard it is for current to flow

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26
Q

what happens in a series circuit when a resistor is added

A

The total resistance of the circuit increases the pathway becomes harder for current to flow

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27
Q

ohms law

A

the electric current through a conductor between two points is directly proportional to the voltage across the two points

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28
Q

Explain if a resistor obey ohms law

A

A resistor obeys ohms law because the two variables in direct proportion because the resistance stays the same

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29
Q

filament lamp in a circuit - current, potential difference, resistance, does it obey ohms law?

A
  • The current causes the filament to heat up and glow
  • The greater the potential difference the more current flows and the hotter and whiter the filament gets
  • resistance increases as temp of filament increases
  • goes against ohms law
30
Q

doide in a circuit - current, potential difference, resistance, does it obey ohms law?

A
  • diode has low resistance if the potential difference is in one direction meaning the current can only flow in the other direction
31
Q

Light dependent resistor (LDR) - resistance?

A

As high resistance in the dark, but the resistance get smaller when the light intensity increases

32
Q

thermistors - resistance?

A

Higher resistance at low temperatures, but as the temperature increases, the resistance decreases

33
Q

Why does the resistor become warm?

A
  • because when a current passes through a resistor energy is transferred because electrical work is done against the resistance
  • the energy is transferred by heating and resistor becomes warm
34
Q

explain how a resistor works and causes resistance

A
  • as the electrons flow through the lattice of vibrating ions, they collide with the ions
  • The more collisions they make with the ions the harder is for them to pass through to the higher the electrical resistance
  • When the electrons collide with the ions they transfer energy to them
35
Q

How can resistance be reduced? (2)

A
  • By using wires made from metals with low resistance
  • by cooling metals so that the lattice ions are not vibrating as much
36
Q

What is a metal with low resistance?

A

copper

37
Q

Power

A

The energy transferred per second
- Rates at which energy is delivered

38
Q

how to work out power

A

Power = energy transferred / by time taken

39
Q

electrical power equations

A

Electrical power = Current x potential difference
Electric power = current squared x resistance

40
Q

electrical power

A

The rate at which electrical energy is transferred in a ciruit

41
Q

Direct current

A
  • An electric current that is in one direction so the flow of charge is always in the same direction
  • Cells and batteries have a positive and negative terminal and the direction of the movement of charge stay the same
42
Q

how is mains electricity produced?

A

Mains electricity is produced using generators that rotate causing the direction of the current keep changing

43
Q

Alternating current

A

a current in which the direction of the flow of electrons which is back-and-forth at regular intervals or cycles
-> the voltage also changes increase into a peak voltage then decreasing into 0 - it then increases to pee in the opposite direction before decreasing back to 0 - this cycle repeats

44
Q

what is the power rating of an appliance measured in

A

watts

45
Q

Earth wire

A
  • Connected to metal parts of the appliance to a large metal spike or metal tubing that is pushed into the ground
  • It is for safety and is at 0 V if the circuit is correctly connected
46
Q

neutral wire

A

The return path to the power station

47
Q

fuse

A

A safety device marked with the current it can carry

48
Q

Live wire

A

Connect the appliance to the generators at the power station

49
Q

fuse function

A
  • when the current passes through the wire the wire gets hotter
  • If the current exceeds a certain value then the wire melts this breaks the circuit and stops the current
50
Q

reason for an Earth wire

A

if the metal part are at high voltage and you touch the metal, you don’t get an electric shock because the current goes to the ground instead of through you

51
Q

circuit breakers

A
  • alternative to fuses
  • They detect to change in the current and safely switch off the supply
52
Q

advantages of circuit breakers and disadvantages of fuses

A

once the fault is fixed, they can be switched back on whereas fuse has to be replaced
- they work very quickly so I can save lives as a fuse take some time to me and will not prevent you getting a shock if for example you touch a wire

53
Q

what happens if a fault causes the live wire to touch a metal part?

A
  • This makes a very low resistance circuit and causes a large current to flow to the Earth wire which heats up the wire and this could cause a fire
  • If this happens, the car blows the fuse and cuts off the mains electricity supplies
54
Q

what happens if a faulty appliance draws too much current?

A

It can cause overheating of the wire and can cause a fire, however a fuse stops from happening
-> if an appliance develops a fault it’s metal parts can be a high voltage and if you touch the metal you might get a dangerous electric shock. For this reason the metal parts of the appliances are connected to earth wire so that the current goes into the ground instead of through you

55
Q

Insulators

A

A material or an object that does not easily allow electricity to pass through it

56
Q

what happens when you rub an acetate roll with a dry duster?

A

Some of the electrons move from the acetate onto the duster

57
Q

what happens when you rub a polythene rod with a duster

A

Electrons move from the duster onto the polythene rod

58
Q

what happens if two objects have opposite charges

A

There is a force of attraction between the two object

59
Q

What happens if two objects have the same charge?

A

The objects repel each other

60
Q

Static electricity

A

When the charge is not able to flow away from the surroundings - they all have the same charge and they all repel each other

61
Q

Charging by induction

A

A process that charges an object without touching it to another charged object
-> it involves bringing a charge object close to an uncharged conductive material that is grounded. The result is that the conductor has a charge opposite to the charge object.

62
Q

How do you prevent a spark between a fuel pipe and an aircraft?

A

There’s a bonding line connected to the aircraft before fuelling begins

63
Q

Why do buildings have lightning conductors?

A

To discharge clouds safely - clouds have static electricity due to the friction between the particles of ice or water moved by air currents

64
Q

what happens in electric static spraying for crops?

A
  • when spraying crops with insecticide, electrodes on the sprain nozzle charge the spray droplets as they pass
  • The droplets spread out because they repel each other and then they’re attractive to the plants by induction
  • this means that the spray spreads around the plant even underneath it
  • less spray falls in the ground and farmers don’t use as much
65
Q

force field

A

the volume of space around an object in which another object can experience a force

66
Q

magnetic field

A

a magnet has a force field

67
Q

electric field

A

A charge of an object has a force field around it

68
Q

field lines

A
  • never cross
  • show where the field is strongest (which is where the field lines are closest together)
  • show the direction of the force on a charge in the field
  • start on a positively charged object and ends on a negatively charged object
69
Q

point charge

A

a theoretical electric charge that is located at a single point in space

70
Q

electric field between two parallel points

A

it’s uniform - it is the same in all places between the two points

Physics GCSE (9 decks)

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