ELECTRICITY Flashcards

1
Q

The greater the resistance across a component….

A

the smaller the current that flows( for a given potential difference across the component

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2
Q

CHARGE FLOW =

A

CURRENT* TIME

Q=IT

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3
Q

POTENTIAL DIFFERENCE =

A

CURRENT * RESISTANCE

V=IR

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4
Q

factors that affect resistance

A

length

if the circuit is in series or parallel

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5
Q

what type of resistance do ohmic conductors have

A

they have a constant resistance

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6
Q

Does the resistance of ohmic conductors change with current

A

No

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7
Q

when an ohmic conductor is at a constant temperature

A

the current flowing through it is directly proportional to the potential difference flowing through it

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8
Q

what is an LDR (2 points)

A

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

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9
Q

what happens to the resistance of an LDR in bright light

A

the resistance falls

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10
Q

what happens to the resistance of an LDR in darkness

A

the resistance is highest

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11
Q

what can you use LDRs for

A

automatic night lights
outdoor lighting
burgular detectors

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12
Q

what is a thermistor

A

A thermistor is a temperature dependent resistor

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13
Q

what happens to the resistance of a thermistor in hot conditions

A

the resistance drops

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14
Q

what happens to the resistance of a thermistor in cool conditions

A

the resistance goes up

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15
Q

where can you use thermistors

A

they can be useful temperature detectors
car engine temp sensors
electronic thermostats

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16
Q

how are the components connected in a series circuit

A

the components are connected in a line, end to end between the power supply
the voltmeters in a series circuit are always connected in PARALLEL

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17
Q

what happens if you disconnect one component in a series circuit

A

the circuit is broken and they all stop

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18
Q

Potential difference is _________________ in a series circuit

A

the Potential difference is shared between the various components

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19
Q

potential difference in a series circuit will always add up to the __________

A

the source potential difference

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20
Q

Equation for potential difference connected in series

A

Vtotal= V1 + V2 + V3 …..

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21
Q

Current in a series circuit is ________

A

the same through all components

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22
Q

Equation for current connected in series

A

I1=I2=I3=I4

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23
Q

In a series circuit the total resistance of two components is the _______ of their resistances

A

sum

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24
Q

when a resistor is added to a series circuit what happens to the current and resistance

A

the total current is reduced and the resistance is increased

25
Q

in a series circuit cell potential difference (V) ______

A

adds up

26
Q

How are components connected in a parallel circuit

A

each component is connected separately to the power supply

27
Q

What happens if you remove components in a parallel circuit

A

Hardly anything will happen to the cirucit

28
Q

In a Parallel circuit Potential difference is ________

A

the same across all components

29
Q

will identical bulbs connected in parallel be at the same brightness

A

yes because potential difference is the same across all components

30
Q

In parallel circuits total current is ______________

A

is shared across the separate components

31
Q

what does adding a resistor to a parallel circuit do to the resistance and the current

A

it decreases the resistance and it increases the current

32
Q

What type of current is mains supply

A

AC current

33
Q

What type of current is battery supply

A

DC current

34
Q

how are alternating currents produced

A

they are produced by alternating voltages in which the negative and positive ends keep alternating

35
Q

what voltage is the uk mains supply

A

230V

36
Q

what is the frequency of the ac mains supply

A

50 Hz

37
Q

what is dc current and how is it created

A

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

38
Q

Colour of live wire

A

brown

39
Q

colour of neutral wire

A

blue

40
Q

colour of earth wire

A

green and yellow

41
Q

purpose of the live wire

A

provides the alternating potential difference at about 230V

42
Q

purpose of neutral wire

A

the neutral wire completes the circuit and carries away current its around 0V

43
Q

purpose of earth wire

A

it is for protection, it stops the appliance casing from becoming live its at 0V

44
Q

when do earth wires carry current

A

when there is a fault

45
Q

why can a live wire give you an electric shock

A

your body is at 0V this means that if you touch the live wire a large amount of potential difference is produced across your body and current flows through you. This causes an electric shock

46
Q

can you still get an electric shock if the plug socket or switch is turned off

A

yes because there is still potential difference in the live wire, so if you make contact with the live wire your body would provide a link between the supply and the earth so current will flow through you.

47
Q

equation for power in electrical appliances

A

ENERGY = POWER * TIME

E=PT

48
Q

What does the power rating tell you

A

power rating tells you the amount of energy transferred between stores per second

49
Q

the lower the power rating…

A

the less electricity an appliance uses in a given time so its cheaper to run

50
Q

equation for energy transferred in a circuit

A

ENERGY= CHARGE FLOW*POTENTIAL DIFFERENCE

E=QV

51
Q

Equation for power in an appliance

A

power= potential difference * current

p=VI

52
Q

EQUATION FOR POWER WHCIH INVOLES CURRENT AND RESISTANCE

A

P=I2R

53
Q

What does the national grid use ( pd and Current)

A

they use a high pd and low current

54
Q

what do step up and step down transformers do

A

step up transformers increase the potential difference

step down transformers reduce the potential difference for domestic use

55
Q

why is the national grid efficient at transferring energy

A

the national grid distributes electricity at a high pd and low current. a high pd means that it can distribute lots of power per second. using a low current reduces energy losses which makes the national grid efficient at transferring energy

56
Q

Jake removes his jumper in a dark room he hears a crackling noise and sees tiny sparks between his jumper and his shirt explain

A

as the jumper rubs against the shirt a static charge builds up between the jumper and the shirt this is due to the electrons being removed from one and being deposited onto the other. The charge becomes large enough for electrons to jump across the small air gap between the jumper and the shirt causing sparks

57
Q

what direction are the field lines on a positively charged isolated sphere

A

outwards

58
Q

what direction are the field lines on a negatively charged isolated sphere

A

inwards