# Physics- Electricity

version from 2015-05-11 17:00

## Section

What carry electrical charge around the circuitElectrons
How do electrons flowDelocalised electrons are attracted towards the +ve terminal of the battery cell as they have -ve charge.
Define currentThe rate of flow of electrons
Equation for currentI=Q/T
Unit for currentAmps
Unit for chargeCoulombs
In a series circuit, how much current is there around the circuitThe current is same everywhere
What does the current flowing into a junction equal toThe current flowing out of the junction
Equation for voltageV=E/Q
Unit for voltageVolts
Unit for energyJoules
How much voltage is there in a series circuitThe total circuit component voltages equals to the battery voltage
How much voltage is there in a parallel circuitThe total circuit component voltages across each branch equal to the battery voltage.
What is the correlation between resistance and lengths of wire and whyThe longer the lengths of wire, the greater the resistance. This is because the electrons have further to travel so they will collide with metal ions more frequently.
What is the correlation between resistance and cross- sectional area and whyThe greater the cross- sectional area, the smaller the resistance. This is because more electrons have more routes to travel.
Equation for resistanceR=V/I
Unit for resistanceOhms
What is the correlation between resistance and current in a bulb and whyAs the resistance increases, the current increases. This is because as the current increases, there is a higher temp. which means particles will collide more frequently as the metal ions are vibrating more.
What are diodesThey only allow current to flow in one direction which is direction arrow is facing. For the circuit to work, the arrow has to be facing the -ve terminal.
What are thermistorsComponents whose resistance changes with temp. As the temp. increases, the resistance decreases as the electrons move quicker.
What are light dependant resistorsComponents whose resistance changes with light intensity. As the light intensity increases, the resistance decreases.
Define powerRate at which energy is transferred
Equation for powerP=I*V
Unit for powerWatts
Equation for energyE=P*t
What type of current does mains electricity emitAlternating current
What are fusesComponents that prevent too much current flowing through the circuit. They also prevent the possibility of overheating and fires. They manage to do this because they have ratings in amps which if the current exceeds, the fuse will melt.
What fuse should you useYou should use a fuse which has a slightly higher rating than the current flowing through the circuit
What are earth wiresThey are connected to the metal casing and prevent people from receiving shocks
What are double insulated appliancesThey have plastic casings which are insulators so they don't need earth wires. The insulator removes the risk of receiving shocks.
Equation for peak voltageVolts per division * divisions
Equation for time periodms per division * divisions
Equation for frequencyF=1/t
Unit for frequencyHertz
Define large potential differenceA large charge difference between two charges
How can you prevent sparkBy attaching metal from earthing object to ground
What causes insulators to be chargedFriction