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PHYSICS-EVIE > Topic 2-electricity > Flashcards

Topic 2-electricity Flashcards

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1
Q

whats current

A

a flow of electrical charge

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2
Q

what does a current rely on to flow round a complete closed circuit

A

potential difference

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3
Q

whats the unit of current

A

ampere (A)

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4
Q

when does the current have the same value everywhere

A

in a single closed loop

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5
Q

what does potential difference (voltage) do

A

pushes the charge around

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6
Q

whats the unit of potential difference

A

volt(V)

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7
Q

whats resistance

A

anything that slows the flow down

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8
Q

whats the unit of resistance

A

ohm

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9
Q

give the link between current and resistance

A

The greater the resistance across the component the smaller the current that flows

for a given potential difference across the component

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10
Q

how does a large amount of charge flow around a circuit

A

when a larger CURRENT flows

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11
Q

what can the resistance of the circuit depend on

A

whether components are series or parallel or the length of wire use in the circuit

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12
Q

give examples of ohmic conductors

A

wire or resistors

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13
Q

what thing does the resistance NOT change with the current

A

ohmic conductors

ata a constant temperature the current flowing through ohmic conductor is directly proportional to the potential difference across it

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14
Q

in what components does the resistance change

A

diodes and filament lamps

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15
Q

what happens when a filament lamp is used in a circuit

A

we the current increases the filament lamp heats up more and the resistance increases

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16
Q

what happens with diodes in circuits in terms of resistance

A

they will allow the current to flow in one direction but have a very HIGH resistance if it is reversed

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17
Q

whats LDR short for

A

light dependent resistor

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18
Q

what’s an ldr

A

a resistor that is dependent on the intensity of light

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19
Q

what does resistance do with ldr

A

in bright light the resistance falls

in darkness the resistance is highest

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20
Q

What are LDRs used for

A

automatic night lights outdoor lighting and burglar detectors

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21
Q

What’s the thermistor

A

Temperature dependent resistor

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22
Q

describe resistance with a thermistor

A

hot conditions -low resistance

cool conditions- resistance goes up

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23
Q

example of thermisters

A

Car engine temperature sensors and electronic thermorstats

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24
Q

What is sensing circuits used for

A

turn on or increase the power to components depending on the conditions that they are in

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25
Q

The bigger the components resistance….

A

The more of the PD it takes

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26
Q

describe features of series circuits

A
  • The different components are connected in a line, end to end between the positive and negative of the power supply
  • if you remove or disconnect one component a circuit is broken and they all stop
  • The total potential difference of the supply is shared between the various components ( V total = V1+ V2 +…..)

*current is the same everywhere
(I1=I2=….)

  • resistance adds up (R total=R1+ R2)
  • Cell potential differences add up
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27
Q

Describe the features of parallel circuits

A
  • each component is separately connected to the negative and positive of the supply
  • potential difference is the same across all components which means identical bulbs will be at the same brightness (V1=V2=…)
  • current is shared between branches (I total= I1+ I2+…)
28
Q

what happens when you add resistors in series

A

The total resistance increases and the current decrease

29
Q

What happens when you add resistors in parallel

A

Total current increases total resistance decreases

30
Q

What are the two different types of electricity supply

A

Alternating and direct

31
Q

Main supply is

A

A/C

32
Q

Battery supply is

A

DC

33
Q

What does the current to do in AC supplies

A

It’s constantly changing direction

the current is produced by alternating voltages in which the p and n ends keep alternating

34
Q

What is direct current

A

A current that is always flowing in the same direction created by direct voltage

35
Q

What coats wires

A

The core of copper and coloured plastic coating

36
Q

Describe the live wire

A

Brown

provides alternative potential difference from mains-supply

37
Q

Describe the neutral wire

A

Blue

complete the circuit and carries away current

electricity normally flows in through the livewire and out through the neutral wire

38
Q

describe the earth wire

A

Green and yellow
protects wiring
safety
stops appliance casing from becoming live
doesn’t carry current only when there is a fault

39
Q

What is dangerous about a plug

A

Any connection between life on earth can be dangerous
if the link creates a little resistance path to earth a huge current will flow which could result in a fire

electric shock (current flows theough you)

40
Q

what is energy transferred from

A

cells and other sources

41
Q

What does a moving charge do

A

Transfers energy because the charge does work against the resistance of the circuit

42
Q

Describe the energy transfer in the kettle

A

They transfer energy electrically from the mains supply to the thermal energy store of the heating element inside the kettle

43
Q

Describe energy transfers in an electric fan

A

Energy is transferred electrically from the battery of a handheld fan to the kinetic energy store of the fans motor

44
Q

What does the total energy transferred by an appliance depend on

A

How long it’s on for and its power

45
Q

What’s the power of an appliance

A

The energy that are transfers per second

46
Q

water appliances often given

A

A power rating

47
Q

What is potential difference

A

Energy transferred per charge passed

48
Q

When energy is transferred what has taken place

A

Electrical charge goes through a change in potential difference

49
Q

What’s the National Grid

A

Giant system of cables and Transformers that covers the UK and connect the power stations to consumers

50
Q

How does the National Grid transmit the huge amount of power needed

A

Boost to the potential difference up really high and keep the current as low as possible

increasing the potential difference decreases the current which decreases energy loss by heating the wires and the surroundings which makes it efficient

51
Q

How does the potential difference get to 400,000 V

A

Transformers are used which step up the potential difference at one end for efficient transmission then bring it down to safe useable levels

big pylons with huge insulators are also used

52
Q

What’s static electricity

A

all about charges which are not free to move

example insulating materials

53
Q

what happens when polythene rod and cloth duster are rubbed together

A

electrons move from the duster to the rod

the rod becomes negatively charged and the duster becomes positively charged

54
Q

what happens if if you rub an acetate plastic rod with a duster

A

electrons move from the rod to the duster

the duster becomes negatively charged and the rod becomes positively charged

55
Q

what only moves electrons or protons

A

electrons

56
Q

How was the spark caused by static electricity

A

as Electric charge builds on an object, the potential difference between the object and the Earth increases

if the potential difference gets large enough electrons can jump across the gap between the charged object and the Earth

they can also jump to any earth conductor just nearby

57
Q

What’s electrostatic attraction and repulsion

A

Where opposite electric charges are attracted and same electric charges are repelled

58
Q

when is an electric field created

A

Around any electrically charged object

59
Q

closer to the object you get…

A

the stronger the field is

and visa versa

60
Q

How do you draw the field lines for an isolated charged sphere

A

Electric field lines go from positive to negative
there always at a right angle to the surface

the closer together the lines are the stronger the field is

61
Q

As you increase the distance between the charged objects…

A

The strength of the field decreases and the force between them get smaller

62
Q

When are sparks caused

A

When there is a high enough potential difference between a charged object and the Earth

63
Q

What’s ionisation

A

When the strong electric field causes electrons in the air particles to be removed

64
Q

What does the high potential difference cause

A

A strong electric field between the charged object and the Earth object

65
Q

What happens when air is ionised

A

It’s normally an insulator but when it’s ionised it is much more conductive so the current can flow through it

PHYSICS-EVIE (1 decks)

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