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Eleanor Rowe Physics > Electricity Content > Flashcards

Electricity Content Flashcards

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1
Q

What is potential difference?

A

The driving force that pushes the charge round the circuit

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2
Q

What is resistance

A

Anything that slows the flow down

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3
Q

What is electric current

A

A flow of electric charge

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4
Q

Finish the sentence: the greater the resistance….

A

The smaller the current that flows

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5
Q

What does the total charge through a circuit depend on?

A

The current and the time

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6
Q

True/false: more charge passes around they circuit when a smaller current flows

A

False, more charge passes around the circuit when a larger current flows

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7
Q

What things can have an effect on the resistance in a circuit?

A

Whether the components are in series or parallel, or the length of wire used in a circuit

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8
Q

What is an ammeter and what must you do with it when measuring?

A

Ammeter is something that measures current

It must be placed in series with whatever you’re investigating

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9
Q

What does a voltmeter measure and what must you do with it when measuring this

A

It measures the potential difference

Must be placed in parallel around whatever you’re investigating

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10
Q

True or false: resistance is directly proportional to length, the longer the wire, the greater the resistance

A

True

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11
Q

What is an ohmic conductor?

A

A wire or a resistor

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12
Q

Does the resistance of an ohmic conductor change with the current?

A

No

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13
Q

What does the term IV characteristic mean?

A

It refers to a graph which shows how the current flowing through a component changes as the potential difference across is it increased.
Different components have different Iv characteristics

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14
Q

What does the IV graph for an ohmic conductor (eg resistor at a constant temperature) look like and why?

A

Straight line

The current is directly proportional to the pd

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15
Q

What does the IV graph look like for a filament lamp?

A

A curved/wavy line

Because as the current increases, the temperature increases.

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16
Q

What does the IV graph for a diode look like and why?

A

Steep line in only top right half of graph

Current will only flow though diode in one direction, it has a very high resistance

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17
Q

Facts about a LDR ( Light dependent resistor)

A

In a bright light, the resistance falls
In darkness, the resistance is the highest
They have lots of applications including automatic night lights

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18
Q

Facts about a thermistor

A

A thermistor is a temperature dependant resistor
In hot conditions the resistance drops
In cool conditions the resistance goes up
They make useful temperature detectors

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19
Q

What is a series circuit

A

A circuit where all the components are connected in a line, end to end.

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20
Q

If you remove or disconnect a component in a series circuit, what will happen?

A

The circuit is broken and will stop.

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21
Q

What is the rule for potential difference in a series circuit?

A

The total pd of the supply from the battery/cell is shared between the various components, so the pd round s series circuit always adds up to equal the battery/cell pd

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22
Q

What is the rule for current in a series circuit

A

The same current flows through all components

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23
Q

What is the rule for resistance in a series circuit?

A

The total resistance of two components is the sum of their resistances
This is because by adding a resistor in series, the two resistors have to share the total pd

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24
Q

Do cell pd’s add up in series circuit?

A

Yes

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25
Q

How are components connected to the battery/cell in a parallel circuit?

A

They are separately connected to the cell except ammeters which are connected in series

26
Q

What happens if you remove or disconnect a component in parallel?

A

It won’t effect any other components

27
Q

What is the rule for potential difference in a parallel circuit

A

All components have the same pd

28
Q

What is the rule for current in parallel circuits

A

The total current flowing around the circuit is equal to the total of all the currents through separate components
The current is shared between branches

29
Q

What is the rule for resistance in a parallel circuit

A

By adding a resistor the total resistance is dropped

This is because it increases the circuit as another branch is being added on

30
Q

What happens when you add more resistors in a series circuit?

A

It increases the total resistance of the circuit

31
Q

What happens when you add more resistors in a parallel circuit

A

The smaller the overall resistance becomes

32
Q

What are the two types of electricity supply?

A

Alternating current and direct current

33
Q

What is an alternating current?

A

A current that is constantly changing direction, the positive and negative ends keep alternating

34
Q

What supply of electricity is the U.K. mains supply?

A

AC

Alternating current

35
Q

What is the frequency of the ac mains supply?

A

50 Hz( hertz)

36
Q

What things supply direct current?

A

Cells and batteries

37
Q

What is direct current?

A

A current that is always flowing in the same direction

Created by a direct voltage

38
Q

What are the three types of wire in a cable?

A

Live wire
Neutral wire
Earth wire

39
Q

What colour is a live wire

A

Brown

40
Q

What colour is an earth wire

A

Green and yellow

41
Q

What colour is a neutral wire

A

Blue

42
Q

What does a live wire do?

A

Provides an alternating potential difference from the mains supply

43
Q

What does the neutral wire do

A

Completes the circuit and carries away current, electricity flows out of it

44
Q

What does the earth wire do

A

Protects the wiring
Stops the appliance from becoming live
Doesn’t carry a current

45
Q

What are the potential differences of live, neutral and earth wires?

A

Live wire 230V

Neutral and earth 0V

46
Q

What would happen to your body if you touched a live wire?

A

You get an electric shock

Your body provides a link between the supply and the earth, so a current would flow through you

47
Q

What energy transfers occur in a kettle?

A

Transfers energy electrically from the mains ac supply to the thermal energy store of the heating element inside the kettle

48
Q

What energy transfers occur in a handheld fan

A

Energy is transferred electrically from the batter of the fan to the kinetic energy store of the fans motor

49
Q

What does the energy transferred depend on?

A

How long the appliance is on for and it’s power

50
Q

What is a power rating of an appliance?

A

The maximum safe power they can operate at

51
Q

What is the national grid

A

A giant system of cables and transformers that covers the U.K. and connects power stations to consumers

52
Q

How does the national grid transmit the huge amount of power needed?

A

It uses a high pd and a low current

53
Q

When transferring energy through wires, why is the energy changed to a high pd and low current?

A

To make it more efficient so it doesn’t lose energy through a high current to heat

54
Q

What does a step up transformer do in the national grid?

A

Decreases the current and increases the pd

55
Q

What does a step down transformer do in the national grid

A

Increases the current and decreases the pd

56
Q

What is static electricity?

A

Charges caused by friction that are not free to move

They build up and end with a spark or a shock when they do finally move

57
Q

What happens when certain insulating materials are rubbed together and what does this cause the material to become

A

Negative electrons will be scraped off and dumped on the other
The materials are electrically charged, one positive and one negative

58
Q

True/false only electrons produce positive or negative charges in materials

A

True

59
Q

How is a spark caused?

A

When an electric charge builds up in an objectC the pd between that and the earth increases
If the gap gets big enough, electrons can jump across the gap and a spark is produced

60
Q

Facts about electric fields

A

Created around an electrically charged object
The closer to the object you get the stronger the field is
Can be shown by drawing field lines

61
Q

Facts about electric field lines

A

Drawn at a right angle to the surface

Closer together the lines are the stronger the field is

Eleanor Rowe Physics (11 decks)

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