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Physics > P2-Electricity > Flashcards

P2-Electricity Flashcards

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1
Q

What is static electricity?

A

Electric charge stored on insulated objects that doesn’t move

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2
Q

List the particles in an atom and their respective charges

A

Proton +1
Electron -1
Neutron 0

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3
Q

What is a charged atom called?

A

An ion

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4
Q

What materials can be charged by friction?

A

Insulators

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5
Q

When rubbing a polythene rod and a cloth what item becomes negative (gains electrons) and what item becomes positive (loses electrons) ?

What causes this?

A

Polythene Rod-Negative
Cloth-Positive

Friction (the triboelectric effect)

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6
Q

Why does a polythene rod gain electrons when rubbed by a cloth bot a perspex rod loses electrons?

A

As a polythene rod has a higher electron affinity-attracts electrons better, higher up in the triboelectric series.

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7
Q

What type of force occurs between two charged objects?

A

Non contact force

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8
Q

Fill in the blanks:
Like charges_______
Opposite charges_______

A

Repel
Attract

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9
Q

What charge creates an electric field going away from itself

A

Positive

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10
Q

What charge has an electric field going towards itself

A

Negative

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11
Q

Describe electric field lines:

A
  • They can’t cross they can only bend
  • They want to be as short as possible
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12
Q

What does increasing the density of an electric field do?

A

It increases its strength

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13
Q

What does a Van de Graaff generator do?

A

It removes electrons from anything touching it to produce a positive charge

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14
Q

What would happen to a person touching a Van de Graaff generator?

A

Their hairs of the person would stand up on end as the body of the person is all positively charged meaning that the hairs would be repelled

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15
Q

What is the difference between a radial and uniform field?

A

Radial field-from one point
Uniform field-the lines are straight, neat and ordered usually from one plate to another

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16
Q

From what terminal do electrons flow from and to in a cell?

A

from negative to positive

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17
Q

What are multiple cells called?

A

A battery

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18
Q

What does a cell do?

A

Pushes electrons around a circuit

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19
Q

What does a switch do?

A

Enables the current in a circuit to be switched on or off

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20
Q

What does an indicator such as a bulb do?

A

An indicator (such) as a bulb emits light as a signal that current is passing through the circuit

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21
Q

What does a diode do?

A

Allows current to flow in only one direction

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22
Q

What does a light emitting diode (LED) do?

A

Allows current to flow in only one direction and emits light when a current is passing through it

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23
Q

What is an ammeter used for?

A

It is used to measure electric current

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24
Q

What is a voltmeter used for?

A

It is used to measure potential difference

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25
Q

What does a resistor do?

A

It limits the current in the circuit-provides resistance

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26
Q

What does a variable resistor do?

A

It can change the resistance of a circuit

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27
Q

What does a thermistor do?

A

It decreases resistance as the temperature increases

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28
Q

What does a light dependent resistor (LDR) do?

A

It decreases resistance as light levels increase

29
Q

What does a fuse do?

A

A fuse is designed to melt if the current in a circuit gets too high

30
Q

How do you draw a wire in a circuit?

A

You draw it as a straight line or if it needs to change direction at a perpendicular

31
Q

What materials are wires made from and covered with?

A

Copper as it is a good, cheap conductor and they are coated in plastic to insulate them

32
Q

How do you draw /connect a voltmeter in a circuit as opposed to other components

A

You draw /connect it in parallel to a component as oppose to everything else which is in series-this is to measure the difference in energy before and after a component

33
Q

What is the formula linking charge flow, current and time?

A

charge flow = current x time
Q = It

34
Q

What is the unit of measurement used for charge flow?

A

couloums
C

35
Q

What is the unit of measurement used for current?

A

amperes (amps)
A

36
Q

What is the formula linking potential difference, energy transferred and charge?

A

potential difference = energy transferred/charge
V = E/Q

37
Q

What is the unit of measurement for energy transferred?

A

joules
J

38
Q

What is the unit of measurement for potential difference?

A

volts
V

39
Q

What is the formula for resistance?

A

resistance = potential difference/current
R = V/I

40
Q

What is the unit of measurement for resistance?

A

Ohms
Ω

41
Q

What is potential difference?

A

The measure of energy given to the charge carriers in a circuit

42
Q

What is current?

A

The amount of charge carriers in a circuit over a given time

43
Q

What is resistance?

A

The opposition in an electrical component to charge

44
Q

What does increasing the length of a wire do to it’s resistance and why does this happen

A

The resistance increases due to the electrons colliding in more wire-this increases the temperature of the wire meaning that energy is transferred to a thermal source.

45
Q

What causes a short circuit?

A

A short circuit is caused by a shorter route in a circuit (usually by wires touching) and electrons will cause a blockage

46
Q

Describe the relationship between potential difference and current if the resistance is constant.

A

There is a positive correlation between potential difference and current as well as them being directly proportional

47
Q

Describe the relationship between potential difference and current in a circuit with filament lamp

A

There is still a positive correlation between potential difference and current but current increases proportionately less as oppose to the voltage due to resistance increasing via thermal energy of the filament lamp

48
Q

Describe the relationship between potential difference and current in a circuit with a diode.

A

Above 0 there will be a proportionate positive correlation. Below 0 only the voltage will decrease as the current will be blocked and is only allowed to flow one way due to the diode

49
Q

What is a series circuit?

A

Where there is only one path for electrons to flow in a circuit

50
Q

In a series circuit what are the rules for?

1)Current
2)Potential difference
3)Resistance

A

1)Current-Isn’t split between components
2)Potential difference-Is shared between components
3)Resistance-Equal to sum of resistance for each component :
Total resistance = R₁ + R₂

51
Q

What is a parallel circuit?

A

Where there is multiple paths for electrons to flow in a circuit

52
Q

In a parallel circuit what are the rules for?

1)Current
2)Potential difference
3)Resistance

A

1)Current-is split between the number of possible paths to the cell
2)Potential difference-isn’t split between components
3)Resistance-If resistors are connected in parallel the supply current is divided between them. The overall resistance is reduced as the current may follow multiple paths.

53
Q

What is Ohm’s law?

A

Electric current is proportional to voltage provided temperature remains constant and inversely proportional to resistance

54
Q

Describe a domestic electricity supply

A

2 terminals
A direct current
Low potential difference of 1.5-9V

55
Q

Describe a mains electricity supply

A

Has an alternating current-frequency of 50Hz (alternates 50x per second and reaches a peak and a trough of 230 and -230 volts)
Has a much higher potential difference of 230V

56
Q

What are the three wires in a plug and what colours are they?

A
  • Live wire-Brown
  • Neutral wire-Blue
  • Earth wire-Green Yellow striped
57
Q

What does the live wire do?

A

It carries the current

58
Q

What does the neutral wire do?

A

It carries the current back to the original power source

59
Q

What does the earth wire do?

A

It is connected to the ground-provides an easier route for electricity so that if someone accidentally touches the live or neutral wire they won’t be shocked

60
Q

Describe the process in which energy is transferred from power stations to our homes and include the voltage

A

Power station (25KV)->step up transformer->Power lines (132KV)->step down transformer->Factories (33KV) or Homes (230V)

61
Q

What does a step up transformer do and why is this useful?

A

Increase voltage, lowers current which lowers resistance and energy lost-good for transporting energy over large distances

62
Q

What does a step down transformer do and why is this useful?

A

Decrease voltage, Increases current which is safer for household usage

63
Q

What causes a short circuit in a plug socket?

A

The live and the neutral wires touching and this will cause the current to massively increase and cause the fuse inside to blow

64
Q

What measures are there in place to prevent a short circuit in a plug socket?

A

All of the wires are insulated so that they don’t touch

65
Q

What are the pins made of in a plug socket?

A

Brass as they can’t oxidise in an exposed plug and are hard.

66
Q

What is the formula for power?

A

Power = energy transferred/time
P = E/t

67
Q

What Amperage fuses are domestic households fitted with?

A

3A, 5A or 13A

68
Q

What is the formula linking power, current and resistance?

A

power = current² x resistance
P = I² x Ω

69
Q

What is the formula for appliance efficiency?

A

efficiency = output power/input power x 100

Physics (8 decks)

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