electricity Flashcards

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1
Q

current is

A

a measure of the flow of elevtrons around the circuit (Amps A)

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2
Q

Potential Difference

A

force driving flow of electrons
- provided by cell/battery
- voltage (V)

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3
Q

resistance

A

Everything that resists or opposes the flow of electrons
- OHMS

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4
Q

how does current always flow (in convenction current)

A

from the positive to the negative

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5
Q

what equation connects potential diff, resistance and current

A

V = IR

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6
Q

as long as the resistance stays constant

A

as the voltage increses the current will increases proportianally

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7
Q

if we increases the tempreture

A

the resistance would also increases temperature

increases, all of the ions in the metal vibrate faster, which makes it harder for electrons to pass along the wire (or in other words, the resistance increases).

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8
Q

what does diode do

A

it only allows the current flow one way in the circuit by making the resistance towatds the opposite direction too high

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9
Q

what charge is

A

a measure of teh total current that flowed within a centain period of time

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10
Q

what equation connects charge current and time

A

Q = I x T

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11
Q

what si a fuse

A

breaks if too much current ges throught it

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12
Q

differencce between series and parallel circuit

A

series circuit only has one loop and all the components are connected toeach other.
On the other hand parallel circuit contains more tahn one loops.

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13
Q

potential difeference in a series circuit

A

is shared across all of the components

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14
Q

V total (in series)

A

V1 + V2 +…. e.g if total V = 12
and componets 1 V = 6 then comp 2 V = 4

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15
Q

current is series circuit

A

same everywhere in the circuit
- ammemter place in series, anywhere
- volmeter connect in parallel to your component

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16
Q

current calculation

A

I = V (total potential diff) / R (total resistance)

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17
Q

total resistance in seires curcuit

A

= sum of individual reisistance of each components

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18
Q

how to calc the voltage acroos a single componet

A

current X resistance across that specific component

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19
Q

ohms law

A

componets with a greater reisistance will always have a higher share of the voltage

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20
Q

one rreason parallel is better than series

A

if one componet in the parallel breaks then the overall circuit still works

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21
Q

V total in parallel

A

V1=V2=V3 …

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22
Q

I in parallel

A

I total = I1 + I2+ I 3….

23
Q

the more componenets we add in parallel =

A

lower total resistance

24
Q

recall 3 energy formulas

A

Formula 1:

Energy (E) = Power (P) x Time (t)

Formula 2:

Energy (E) = Voltage (V) x Current (I) x Time (t)

Formula 3:

Energy (E) = Charge (Q) x Voltage (V)

25
Q

recall 2 power formulas

A

Formula 1:

Power (P) = Current (I) x Voltage (V)

Formula 2:

Power = Current2 x Resistance

26
Q

what is a national grid

A

giant network of transformers and wires that spreads accross the country to distribute our electricity

27
Q

how do most power sstations works

A

they create a lot of thermal energy and tehn transfer it into electrical energy

28
Q

when does the electricity demand ususally peaks

A

in the late afternoon around 6 when evergyone comes back from school and start watching tv cooking etc
it is also higher in winter

29
Q

why can we not have a very high current

A

because very high current generate a lot of heat enegry because of the resistance therefore we lose a lot of energy to the surrounding

30
Q

how does the national grid works

A
  • Electric power is generated at a power station.
  • Step up transformers increase the voltage and decrease the current.
  • The electric power is transmitted via the national grid at low current which minimises power loss.
  • Step down transformers decrease the voltage and increase the current near our homes.
  • Electric power is wired into our homes at a voltage that is relatively safe to use.
31
Q

descibe in terms of energy how the electricity is produces

A

Fossil fuel and nuclear power stations work by generating thermal energy. This is used to turn water into steam which can then rise and turn turbines. The kinetic energy of the moving turbines can be converted to electrical energy, which is finally sent out across the national grid.

32
Q

difference between AC and DC

A

alternating current directing of the current is contantly swaping back and forth, (in uk all main supply is AC)
direct current in either - or + charge is always flowing in the same direction

33
Q

what is Hz and V for UK main supplu

A

50Hz and 230V per second

34
Q

what is oscilloscope

A

is a device that displays how voltage changes with time

35
Q

direct current is suplied by

A

cells and batteris

36
Q

what are teh 3 cables in a plug

A

live, neutral and earth

37
Q

how are plug wires made

A

they are made up of copper to conduct electricity and are covered in insulating plastic for safety

38
Q

live wire

A
  • brown
  • provides alternating potential difference
  • 230V
  • electricity flows in to the device thought live
39
Q

neutral wire

A
  • completes the circuit by carrying away current
  • 0v
  • electricity flows out of the device
40
Q

earth wire

A
  • doesn’t carry current
    -0 V
  • stop the appliance casing from becoming live
  • if live wire came loose and touched the casing you can get electric shock
  • provide an alternative pathway for the current to flow away
41
Q

what are surges and what can cause them

A

sudden increases in current

  • when you turn an appliance on or aff
  • a fault in the circuit or applience
42
Q

What do fuses and circuit breakers do

A

break the circuit whenever the current gets too high

43
Q

advantage and disadvantages of fuses

A

adv:
- simple and cheap

dis:
- permanatly broken afetra single surge

44
Q

adv and dis of circuit breakers

A

adv
they cant be permentaly damaged , tehy can eb reset

dis
more expensive than fuses

45
Q

what is earthing

A

when an earth wire provides an alternative pathway , any electricity is diverted thought the earth wire

46
Q

what is double insulation

A

when the entire applience is covered in plastic casing, plastic doesn’t conduct electricity so you can;t get an electric shock

47
Q

what is a static electricity

A

a build up of charge on insulating materials

48
Q

in conductiong materials

A

the electrons can flow back so no charge is ever buil up

49
Q

in insulating material

A

electrons can’ t flow back so the tranfer caused by the friction cause positive static charge on th ematerial that has lost the electrons and negative on teh one that gained

50
Q

what happens if an object just keeps gaining the electrons

A

the size of the zharge will increase therefore the potential difference woudl develove between the charged material and the any earthed object.
If the PD high enogh then the elctrons can jump thought the gap which causes the spark.

51
Q

what direction do the elctric field arrows always go in

A

from positive to negative

52
Q

relashionship betweenn the distance and the strenght of the lectric field

A

the field is strongest close to the particle and it egts weaker the further away you get

53
Q

nothing

A

you are the best