P5 Flashcards
Give an example of an AC (alternating current). - AC potential difference causes current to periodically reverse its direction
Mains
A battery is a __ supply, meaning the potential difference causes current to only flow in one direction
DC (direct current)
Mains supply has a frequency of ___ but has a supply potential difference of __
50Hz
230V
describe the live wire
- brown
- carries alternating potential difference from the supply
- potential difference between the live wire and earth is 230V
- DANGEROUS: touching it and connecting it to the earth causes a person to be electrocuted, so they could die
describe the neutral wire
- blue
- completes the circuit
- potential difference of 0V
Describe the earth wire
- green and yellow stripes
- potential difference of 0V
- only carries current if there’s a fault
- safety feature
National grid-
a system of cables and transformers linking power stations to consumers
What do step up transformers do?
- increase potential difference in the transmission lines
What do step down transformers do?
decrease potential difference to a safer voltage for use in homes
a high potential difference means high/low current
low
What does a low current mean in terms of energy?
- less energy lost through heating wire, so it’s a more efficient way to transfer energy
what the equation linking power, current and resistance?
Power = current2 x resistance
P= I2R
what equation links current, power and potential difference?
Power = potential difference x current
P = VI
The amount of energy an appliance transfers is dependant on…
- how long the appliance is on for
- power of appliance
when a polythene rod is rubbed with a duster, how do electrons move?
- from duster to the rod
- duster: lost electrons = positive charge
- rod: gained electrons = negative charge
