Electricity

Question 1

Charging by friction

Answer 1

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

Question 2

Charging by induction

Answer 2

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

Question 3

Charges

Answer 3

P, +
E, -
N, 0

Question 4

Law of electrostatics

Answer 4

Like charges repel

Opposite charges attract

Question 5

Earthing

Answer 5

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

Question 6

Van de Graaf generator

Answer 6

Large potential difference between some and earth

Spark when near a neutral object

Question 7

Use of eletcrostatics

Car painting

Answer 7

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

Question 8

Use of eletcrostatics

Printers

Answer 8

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

Question 9

Use of eletcrostatics

Photocopiers

Answer 9

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

Question 10

Use of electrostatics

Smoke precipitator

Answer 10

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

Question 11

Dangers of static electricity

Answer 11

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

Question 12

How metals conduct electricity

Answer 12

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

Question 13

Conventional current

Answer 13

+-

Question 14

Battery

Answer 14

Store of chemical potential energy

DC

Question 15

DC and AC

Answer 15

DC, one direction

AC, constantly changing direction at 50Hz

Question 16

Resistance

Answer 16

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

Question 17

Current

Answer 17

Rate of charge flowing through a current

Question 18

Potential difference

Answer 18

How much energy is given to the charges

Question 19

Set potential difference

Answer 19

Resistance increases

Current decreases

Question 20

For a set resistance

Answer 20

Voltage increases

Current increases

Question 21

Ohm’s law

Answer 21

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

Question 22

Ohmic behavior

Answer 22

Constant gradient

Question 23

Non ohmic behavior

Answer 23

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

Question 24

Diode

Answer 24

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

Question 25

Resistance of LDR

Answer 25

Light intensity increases, resistance decreases

Brighter, more electrons get excited and become available for conduction

Question 26

Resistance of thermistor

Answer 26

As temp rises, resistance falls

Hotter, more electrons get excited, available for conduction

Question 27

Length and resistance

Answer 27

Caused by electrons colliding with metal ions

Length increase, electrons have to travel further, collisions will increase, increase resistance

Question 28

Thickness and resistance

Answer 28

Increase thickness of wire, increase SA that electrons can flow
Collisions decrease, resistance falls

Question 29

Electrical energy

Answer 29

Current flows through resistor, electrical energy turned into heat energy
Current causes heating

Question 30

Electrical power

Answer 30

Power=current x potential difference

Question 31

Series circuits

Answer 31

Current is constant

Total resistance is greater than greatest single resistor in loop in series circuit

Question 32

Parallel circuit

Answer 32

Voltage is the same
Current goes through path with least resistance
Total resistance smaller than smallest resistance

Question 33

3 pin plug

Answer 33

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

Question 34

Fuse

Answer 34

On live wire
Safety device, breaks circuit if current is too high
Melts
Fuse higher than current needed
Isolates appliance from mains

Question 35

Earthing

Answer 35

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

Question 36

Double insulation

Answer 36

Double insulation, plastic casing, wires plastic coated

Coat cannot be live, if one layer damaged, still safe

Question 37

Circuit breaker

Answer 37

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

Question 38

Mains electricity

Answer 38

Live, +230V, -230V
Neutral, 0V
Earth safety