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Electricity Flashcards

(38 cards)

1
Q

Charging by friction

A

Electrons moved from 1 insulator to another causing a build up of charge by friction
Negative charges move, smaller mass, on outside of nucleus
Total number of charges are the same

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2
Q

Charging by induction

A

Charged object brought near neutral object, electrons on neutral create a charge on surface of neutral object
Negative moves towards positive charges in charged object
Negative charges move away from charged objects

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3
Q

Charges

A

P, +
E, -
N, 0

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4
Q

Law of electrostatics

A

Like charges repel

Opposite charges attract

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5
Q

Earthing

A

Charge flows back to the earth
Earth soaks up charges
Object becomes neutral

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6
Q

Van de Graaf generator

A

Large potential difference between some and earth

Spark when near a neutral object

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7
Q

Use of eletcrostatics

Car painting

A

Car given negative charge
Paint gun given positive charge
Paint spray repels each other, creates fine, even spread of paint
Car body attracted to paint, no waste

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8
Q

Use of eletcrostatics

Printers

A

Tiny ink droplets forced out of fine nozzle, become charged
Droplets deflected between 2 metal plates, voltage applied to plates
Size and direction of voltage across plates changed so paint drop hits different part of page

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9
Q

Use of eletcrostatics

Photocopiers

A

Charging wire charges drum positively
Light hits photoconductive drum reflected from white paper, charge in drum leaks away
Sprayed with -toner, attracted to + drum
Toner melted by hot wire, fuses to paper

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10
Q

Use of electrostatics

Smoke precipitator

A

Smoke, - passes grid
Attracted to + collecting plates
Drop into collector

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11
Q

Dangers of static electricity

A

Refuelling planes, fuel gains electrons from pipes
Pipe,+
Fuel,-
Resulting voltage, spark, fire

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12
Q

How metals conduct electricity

A

Electrons move energy from battery to component
Metals, delocalised electrons not used in bonding, conduct
Battery moves them

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13
Q

Conventional current

A

+-

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14
Q

Battery

A

Store of chemical potential energy

DC

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15
Q

DC and AC

A

DC, one direction

AC, constantly changing direction at 50Hz

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16
Q

Resistance

A

Measure of reluctance of how difficult it is for current to flow through

17
Q

Current

A

Rate of charge flowing through a current

18
Q

Potential difference

A

How much energy is given to the charges

19
Q

Set potential difference

A

Resistance increases

Current decreases

20
Q

For a set resistance

A

Voltage increases

Current increases

21
Q

Ohm’s law

A

Current through the resistor is directly proportional to voltage across if temp is constant
If temp increases for a wire/resistor, more heat, more KE, harder for charges to go through wire
Test resistor takes energy away from current to stop it over heating
Variable resistor, changes rate of flow of current

22
Q

Ohmic behavior

A

Constant gradient

23
Q

Non ohmic behavior

A

Non constant gradient
Filament bulb
Resistance rises as temp rises
More voltage to bulb, lattice ions vibrate
Harder for charges to flow, resistance rises, current falls

24
Q

Diode

A

Only allows current in one direction
When flowing in opposite direction, infinite resistance
Non ohmic

25
Resistance of LDR
Light intensity increases, resistance decreases | Brighter, more electrons get excited and become available for conduction
26
Resistance of thermistor
As temp rises, resistance falls | Hotter, more electrons get excited, available for conduction
27
Length and resistance
Caused by electrons colliding with metal ions | Length increase, electrons have to travel further, collisions will increase, increase resistance
28
Thickness and resistance
Increase thickness of wire, increase SA that electrons can flow Collisions decrease, resistance falls
29
Electrical energy
Current flows through resistor, electrical energy turned into heat energy Current causes heating
30
Electrical power
Power=current x potential difference
31
Series circuits
Current is constant | Total resistance is greater than greatest single resistor in loop in series circuit
32
Parallel circuit
Voltage is the same Current goes through path with least resistance Total resistance smaller than smallest resistance
33
3 pin plug
3 copper wires with thin filaments so if one breaks, others still work Surrounded in plastic insulator, copper will not oxidise Brass pin, does not oxidise easily Earth, safety Live, connected to switch Cable grip, keeps wire in place
34
Fuse
``` On live wire Safety device, breaks circuit if current is too high Melts Fuse higher than current needed Isolates appliance from mains ```
35
Earthing
If live wire dislodged, touches metal casing Fuse melts, low resistance, vvvv large current through earth and live Appliance isolated from live Earth needed to work, circuit is still live
36
Double insulation
Double insulation, plastic casing, wires plastic coated | Coat cannot be live, if one layer damaged, still safe
37
Circuit breaker
Breaks circuit if current gets too high Safety feature Can be reset easily RCCB Operates faster than fuse, can detect small changes in current More effective at preventing electrocution
38
Mains electricity
Live, +230V, -230V Neutral, 0V Earth safety