electricity Flashcards

1
Q

what is electric current?

A

Electric current is the flow of electrical charge

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2
Q

what is current measured in?

A

amps

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3
Q

what is electrical charge measured in?

A

coulombs

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4
Q

electrical charge equation:

A

charge flow = current x time

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5
Q

what is the resistance of a component?

A

Resistance of a component is the measure of how it resists the flow of charge

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6
Q

the higher the resistance:

A
  • the more difficult for charge to flow

- the lower the current

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7
Q

what is resistance measured in?

A

ohms

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8
Q

what does potential difference tell us?

A

potential difference tells us the difference in electrical potential from one point at a circuit to another

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9
Q

the bigger potential difference across a component:

A
  • the greater flow of charge through

- the bigger the current

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10
Q

what is potential difference measured in?

A

volts

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11
Q

potential difference equation

A

potential difference= current x resistance

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12
Q

what does a current graph show?

A

a current graph shows the relationship between potential difference and current for any component

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13
Q

resistor graph:

A

straight line graph

resistance remains constant

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14
Q

filament lamp graph:

A

indicated by a curved graph

resistance increase as current increases

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15
Q

diodes graph:

A

horizontal line along x axis

no current flows

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16
Q

what happens to the resistance of a thermistor?

A

The resistance of a thermistor the decreases as the temperature increases

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17
Q

what happens to the resistance of an LDR?

A

The resistance of an LDR decreases as light intensity increases

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18
Q

what happens in a SERIES circuit?

A

in a series circuit:
current: STAYS the same
potential difference: SHARED

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19
Q

what happens in a PARALLEL circuit?

A

in a parallel circuit:
current: SHARED
potential difference: NOT shared

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20
Q

what happens if a component in a SERIES circuit breaks or is removed??

A

the rest of the components WILL NOT work

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21
Q

what happens if a component in a PARALLEL circuit breaks or is removed??

A

the rest of a component WILL continue to work

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22
Q

what does the power of a device depend on?

A

The power of a device depends on the potential difference across it and the current flowing through it.

23
Q

a device with higher potential difference will….

A

use more energy per second

more powerful

24
Q

2 equations for POWER

A

power= potential difference x current

power=(current)2 x resistance

25
DIRECT current potential difference:
DIRECT - one is always positive or always negative - > makes current constant
26
when is DIRECT current used?
direct current is supplied by cells and batteries
27
ALTERNATING current potential difference:
ALTERNATING - alternates from positive to negative - > makes current direction alternate
28
when is ALTERNATING used?
alternating current is used in mains electricity
29
what colour is live wire?
love wire is brown
30
what colour is neutral wire?
neutral wire is blue
31
what colour is earth wire?
earth wire is green and yellow
32
components of a plug
- fuse - cable grip - cable - live wire - neutral wire - earth wire
33
when is the earth wire used?
current will only flow in the Earth wire if there is a fault (safety wire)
34
what does the live wire do?
The livewire carries the alternating potential from the supply
35
What does the neutral wire do?
The neutral wire complete the circuit by carrying the current away from appliance
36
what are the V of each wire?
LIVE: 230v NEUTRAL: 0v EARTH:0v
37
what are the dangers of mains electricity?
electric shock can be fatal
38
what happens if u touch a live wire?
if you touch a live wire it creates large potential difference across the body
39
what is power?
Power is the rate at which energy is transferred or work is done
40
2 power equations:
power= energy transferred ————————— time power= work done —————— time
41
what is efficiency?
Efficiency is the ratio of useful energy out to the total energy in
42
efficiency of 0.75 (75%) means...
3/4 =useful | 1/4 =wasted
43
2 efficiency equations:
efficiency= Useful energy transfer ——————————— total energy transfer efficiency= useful power output —————————— total power input
44
what happens when charge flows?
when charge flows - work is done - >which depends on the amount of charge that flows and potential difference
45
2 energy transferred equations
energy transferred= power x time energy transferred= charge flow x potential difference
46
what is the national grid?
The National Grid is a system of cables and Transformers linking power stations to homes and businesses
47
what does the power station do?
power stations transfers the energy supply into electrical energy
48
to make power stations more efficient you...
use a smaller number of large power stations
49
why is using larger power stations more efficient?
using large power stations is more efficient because most power plants use steam turbines which are more efficient at higher steam temperatures
50
what do transmission cables do?
transmission cables transfers electricity
51
what does step up transformers do?
step up transformers increase the potential difference from the powerstation to the transmission cables
52
why are step up transformers good?
they reduce the current which reduces the heating effect caused by the current flowing in the transmission cables
53
what does reducing the heating effect do?
reducing the heating affect reduces energy loss to make the transmission more efficient
54
what does step down transformers do?
Stepdown transformers reduce the potential difference from the transmission cables to a much lower value for domestic use