What do conductors and insulators have
- conductors have a low resistance
- insulators have a high resistance
Calculating p.d equation
V = I x R
Resistors in series
- the total resistance across all the components increases as more components are added
- add the resistors to get total resistance
Resistors in parallel
- the total resistance (net) decreases as more components are added as there are more paths for the current to flow through
- total resistance is calculated by dividing the pd of the cell by the total current for the circuit
What does direct current do
- Flow in one direction only
- on a voltage time graph it would appear as a straight horizontal line
What does alternating current do
- regularly changes direction
- would appear as a curve alternating between positive and negative values on a voltage time graph
Why are copper wires and plastic used
- copper wires are good conductors
- plastic is a good insulator
Function of live wire
- carries the current
- connected to the fuse
Function of a fuse
- contains a thin wire that melts if the current gets too high
- when the current gets too high, the wire melts
- this breaks the circuit and protects appliances
Function of neutral wire
- connects to cable in the wall and completes circuit
Function of earth wire
- provides a low resistance path for the current to flow from the case of the device to the ground if there is a fault
- carries away dangerous currents
Why would some appliances not need an earth wire
- they have been designed so that the live wire cannot touch the casing
- they have plastic casings
- the casing cannot give an electric shock even if the wires inside become loose
What are the fuse ratings
- 3A, 5A, 13A
- if a device works at 3A use a 5A fuse etc
What is the equation that links power voltage and current
P = I x V
