P2 Electricity Flashcards

1
Q

battery

A

two or more cells

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2
Q

current

A

measure of the flow of electrons around the circuit

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3
Q

current measured in

A

amps (A)

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4
Q

potential difference is the force driving the flow of

A

electrons

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5
Q

potential difference is provided by the

A

cell/battery

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6
Q

potential difference is measure in

A

Volts (V)

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7
Q

resistance is

A

everything that resists or opposes the flow of electrons around

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8
Q

resistance is measured in

A

Ohms (Ω)

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9
Q

current always flows from

A

positive terminal to negative terminal (even though it makes no sense)

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10
Q

what is ohm’s law

A

v = i x r

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11
Q

so long as resistance remains constant, potential difference and current are…

A

directly proportional

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12
Q

on current/potential difference graphs, the greater the resistance =

A

the less steep the gradient

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13
Q

temperature increase=

A

resistance increase

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14
Q

what does current increase result in on IV characteristics graph

A

current increase = increase heat = increase resistance = gradient less steep

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15
Q

diodes only allow current to flow

A

in one direction

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16
Q

diodes only show current when potential difference is

A

positive

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17
Q

what do diodes have in the opposite direction so that no current can flow?

A

really high resistance

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18
Q

charge is

A

a measure of the total current that flows within a certain period of time

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19
Q

charge is measured in

A

coulombs (C)

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20
Q

what happens if a component breaks in a series circuit?

A

the whole circuit stops working

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21
Q

how is the potential difference shared in a series circuit

A

across all components

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22
Q

in series circuits, Vtotal =

A

V1 + V2 + V3…

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23
Q

How is current shared in series circuits?

A

Current is the same everywhere

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24
Q

Current is measured by an

A

Ammeter

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25
Ammeters are placed
in series
26
why can ammeters be placed anywhere in series circuit
because current is the same everywhere
27
in series circuits, total resistance =
sum of resistance of each component
28
voltage of single component =
current x resistance of component
29
what are volts measured by
voltmeter
30
voltmeters are connected in
parallel to the component you are looking at
31
components with greater resistance always have
a higher share of the voltage
32
parallel circuits are circuits with
more than 1 loop
33
in parallel circuits, if a component breaks
the overall circuit is still in tact
34
in parallel circuits, the potential difference of components are always the same as the total
Vtotal = V1 = V2 = V3
35
in parallel circuits, the sum of each loops current
adds to the total current that flows
36
In parallel circuits, Itotal =
I1+I2+I3…
37
In parallel circuits, loops that have greater resistance
take a lower share of the current
38
electrical current takes the
path of least resistance
39
more components in parallel=
lower total resistance
40
most power stations generate thermal energy and convert it into
electrical energy
41
power stations often run way below maximum capacity in order to
cope if demand skyrockets
42
power is measured in
Watts (W)
43
why is high current an issue for the transmition of electrical power through the national grid?
high current = lots of heat, resulting in a lot of energy lost to thermal store
44
why is voltage so high on the national grid?
p = v x i and current has to be really low, so voltage must be really high to still have high power output
45
what do step-up transformers do?
increase voltage to 400,000V
46
what do pylons do?
transmit electricity across the country
47
what do step-down transformers do?
reduce voltage to safe levels before electricity reaches towns and cities
48
what is alternating current (AC)
when the direction of current often swaps back and fortn
49
when does alternate current occur?
when potential difference fluctuates between positive and negative
50
what current is mains supply
alternating current
51
mains supply alternates between… at a rate of…
+230V and -230V at a rate of 50Hz
52
direct current remains
either positive or negative the whole time
53
whit direct current, charge is always
flowing in the same direction
54
what displays AC and DC graphs on a monitor
oscilloscopes
55
what colour is the live wire?
brown
56
what colour is neutral wire?
blue
57
what colour is earth wire?
striped green and yellow
58
what are wires in mains supply made of and why?
copper to conduct electricity
59
what must copper wires in mains supply be coated in and why
insulating plastic for safety
60
what does the live wire do?
provides alternating potential difference of 230V
61
what does neutral wire do?
carries away current
62
in terms of the live and neutral wire, what does potential difference do?
flows in through live wire and out through neutral wire
63
in the neutral wire, what potential difference is electricity?
0V
64
what potential difference does earth wire have?
0V
65
what is the purpose of earth wire?
safety: if the live wire comes into contact with the appliance casing, the earth wire stops the casing from having a high voltage by providing an alternate pathway for current to flow
66
difference in voltage causes
electricity to pass from one to the other
67
electricity passes from
high voltage to low voltage
68
why do humans get electrocuted if they touch the live wire?
the live wire has a voltage of 230V and humans have a voltage of 0V, electricity moves from high voltage to the low voltage
69
What sort of resistance do conductors have
very low resistance
70
total resistance of resistors in parallel
is less than the resistance of the smallest resistor
71
mA = milliAmps:
divide by 1000 to get Amps
72
MA = megaAmps:
times by 1,000,000 to get amps