Electricity Flashcards
(38 cards)
Charging by friction
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
Charging by induction
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
Charges
P, +
E, -
N, 0
Law of electrostatics
Like charges repel
Opposite charges attract
Earthing
Charge flows back to the earth
Earth soaks up charges
Object becomes neutral
Van de Graaf generator
Large potential difference between some and earth
Spark when near a neutral object
Use of eletcrostatics
Car painting
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
Use of eletcrostatics
Printers
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
Use of eletcrostatics
Photocopiers
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
Use of electrostatics
Smoke precipitator
Smoke, - passes grid
Attracted to + collecting plates
Drop into collector
Dangers of static electricity
Refuelling planes, fuel gains electrons from pipes
Pipe,+
Fuel,-
Resulting voltage, spark, fire
How metals conduct electricity
Electrons move energy from battery to component
Metals, delocalised electrons not used in bonding, conduct
Battery moves them
Conventional current
+-
Battery
Store of chemical potential energy
DC
DC and AC
DC, one direction
AC, constantly changing direction at 50Hz
Resistance
Measure of reluctance of how difficult it is for current to flow through
Current
Rate of charge flowing through a current
Potential difference
How much energy is given to the charges
Set potential difference
Resistance increases
Current decreases
For a set resistance
Voltage increases
Current increases
Ohm’s law
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
Ohmic behavior
Constant gradient
Non ohmic behavior
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
Diode
Only allows current in one direction
When flowing in opposite direction, infinite resistance
Non ohmic