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GCSE:Physics- CGP Revision Guide -END > P2-Electricity > Flashcards

P2-Electricity Flashcards

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1
Q

What is potential difference

A

Is the driving force that pushes the charge around

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2
Q

what is resistance

A

Is something that slows the flow down

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3
Q

What does the current flowing through a component to depend on

A

Depends on the potential difference across it and the resistance of the component

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

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4
Q

What are ammeters

A

Measures the current flowing through the test wire

The Ammeter must always be placed in series with whatever you’re investigating

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5
Q

What is a voltmeter

A

measures the potential difference across the test wire

The voltmeter must always be placed in parallel around whatever you’re investigating

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6
Q

Why is the IV characteristic of an ohmic conductor like that

A

For some components as the current through them is charged the resistance of the component changes as well

The resistance of ohmic conductor doesn’t change with the current. At a constant temperature of the current flowing through this is directly proportional to the potential difference across it

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7
Q

Why is the IV characteristic of a filament lamp like that

A

When an electrical charge flows through a filament lamp it’s transfers enough energy to the thermal energy store of the filament lamp which is designed to heat up. Resistance increases with temperature so as the current increases the filament lamp heats up more and the resistance increases

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8
Q

Why is the IV characteristic of a Diode like that

A

For diode the resistance depends on the direction of the current. They will happily let current flow in One Direction but have a very high resistance if it is reversed

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9
Q

What does the IV graph for an ohmic conductor look like

A

It goes diagonally across the whole graph through the second and third quarters

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10
Q

What does the IV graph for an filament lamp look like

A

This is a Bendy line through the second and third quarters

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11
Q

What does the IV graph for an diode look like

A

This is a line increasing is deeply in the second quarter

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12
Q

What is an LDR

A

This is the shorthand for light dependent resistor

An LDR is an resistor that is dependent on the intensity of light

The brightest light the resistance falls

The darkest resistance is highest

They have loads of applications including automatic night lights, outdoor lighting and burglar detectors

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13
Q

What is an Thermistor

A

This is a temperature dependent resistor

In hot conditions the resistance drops

In cool conditions the resistance goes up

Thermistors make use for temperature detectors

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14
Q

Water sensing circuits

A

Sensing circuits can be used to turn on or increase the power to components depending on the conditions that they are in

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15
Q

What are series circuits

A

In a series circuits, the different components are are connected in a line, end to end

If you remove or disconnect one component, the circuit is broken and they all stop. This is generally not very handy and in practice very few things are connected in series

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16
Q

What is the potential difference like in a series circuits

A

In series circuits the total potential difference of the supply is shared between the various components. So the potential difference around a series circuit which adds up to equal to source potential difference

17
Q

What’s the current like in a series circuit

A

In series circuit the current flows through all components

The size of the current is determined by the total potential difference of the cells and the total resistance of the circuit

18
Q

What’s the resistance like in a series circuit

A

In series circuits the total resistance of two components it’s just that some of the resistances

This is because by adding a resistor in series the two resistors have to share the total potential difference

The bigger components resistance the bigger share of the total potential difference

19
Q

What is a parallel circuit

A

In Parallel circuits each component is separately connected to the supply

If you remove or disconnect one of them it will hardly affect the others at all

This is obviously how most things must be connected. For example in cars and in household electrics. You have to be able to switch everything on and off

Every day circuits often include a mixture of series and parallel parts

20
Q

What is the potential difference like in a parallel circuit

A

In parallel circuit components get the full source potential difference, so the potential difference is the same across all components

This means that I don’t have boobs connected in parallel will all have the same brightness

21
Q

What is the current like in a parallel circuit

A

In parallel circuits the total current flowing around the circuit is equal to the total of all the Currents through the separate components

In a parallel circuit there are junctions with the current either splits all rejoins. The total current going into a junction has to equal the total current leaving

If two identical components are connected in parallel then the same current will flow through each component

22
Q

Why does adding a resistor in parallel reduced the total resistance

A

In parallel by three sisters have the same potential difference across them as the source

This means the pushing force making the current flow is the same as the source potential difference for each resistor that you add

But by adding another loop the current had more than one direction to go in

This increases the total current that can throw around the circuit. An increase in current means a decrease in the total resistance of the circuit

23
Q

what are the 2 type of electricity supply

A

alternating current (ac)

direct current (dc)

24
Q

what are alternating current supplies

A

the current is constantly changing direction. they are produced by alternating voltages in which the positive and negative ends keep alternating

25
Q

what are direct current supplies

A

is a current that is always flowing in the same direction. it is created by a direct voltage

26
Q

what voltage is the UK mains supply

A

is an ac supply at around 230V

27
Q

what is the frequency of an ac mains supply

A

50 cycles per second or 50Hz

28
Q

what is an example of dc supply

A

cells and batteries

29
Q

what is the meaning of 3 core cables

A

this means that that they have 3 wires inside them each with a core of copper and coloured plastic coating

the colour of the coating shows it purpose

the colours are always the same for all appliances

30
Q

what is the brown wire

A

Live wire

The brown wire produces the alternating potential difference at about 230V from the mains supply

31
Q

what is the blue wire

A

Neutral wire

the neutral wire completes the circuit and carries away the current

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

it is around 0V

32
Q

what is the green and yellow wire

A

It is for protecting the wiring and for safety

it stops the appliance casing from becoming live

it doesn’t usually carry a current but only when there is a fault

it also at 0V

33
Q

how does the live wire give you an electric

A

your body live the earth is at 0V. this means that if you touch the live wire , a large potential difference is produced across your body and a current flows through you

This causes a large electric shock which could injure or even kill you

even if something is off there is a chance of getting an electric shock because there is a potential difference in the live wire

any connection between live and earth can be dangerous. if they link it creates a low resistance path to earth a huge current will flow, which could result in a fire

34
Q

why is potential difference the energy transferred per charge passed

A

when an electric al charge goes through a change in potential difference, then energy is transferred

Energy is supplied to the charge at the power source to ‘rise’ it through a potential

the charge gives up this energy when it falls through any potential drop in components elsewhere in the circuit

that means that a buttery with a bigger pd will supply more energy to the circuit for every coulomb of charge which flows round it because the charge is raised up ‘higher’ at the start

35
Q

how is electricity distributed in the uk

A

this is done by using the national grid

the notional grid is a giant system of cables and transformers that cover the uk and connects power stations to consumers

the national grid transfers electrical power from power station anywhere on the grid to anywhere else on the grid where it is needed

36
Q

when and how does electricity production meet demand

A

throughout the day, electricity usage changes. power stations have to produce enough electricity for everyone to have when they need

they can predict when the most electricity will be used though. demand increases when people get up in the morning, come home form school or work and when it starts to get dark or cold

power stations often run at well below their maximum power output

37
Q

What sort of potential difference and current do the National Grid use

A

To transmit the huge amount of power needed you need a high potential difference or a high current

The problem with a high current is that you lose loads of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings

It’s much cheaper to boost the potential difference up really high (400,000 V) and keep the current as low as possible

For a greater power, increasing the potential difference decreases the current and, which decreases the energy lost by heating the wires and the surroundings. This makes the National Grid an affective way of transferring energy

38
Q

How is the potential difference changed in the National Grid

A

To get the potential difference to 400,000 V to transmit power requires transformers as well as big pylons with a huge installation-but it’s still cheaper

The transformers have to step the potential difference up at one end for efficient transmission and then take it back down to safe, usable levels at the other end

The potential difference is increased (steped up) using a step up transformer

It’s then reduced again (stepped down) for domestic use using a stepdown transformer

GCSE:Physics- CGP Revision Guide -END (7 decks)

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