Supplying Electricity Flashcards
why is the live wire dangerous
provides large P.D. that would cause large current to flow through a person if touched
unit for:
-power
-current
-potential difference
-resistance
-watt (W)
-amp (A)
-volt (V)
-ohm(Ω)
what 2 things does energy transfer to an appliance depend on
-power if appliance
-time it is switched on for
how does having a large P.D. in the transmission cables help to make the national grid an efficient way to transfer energy
a large P.D. means a small current is needed to transfer the same amount of power, small current in transmission cables means less electrical power dissipated to thermal store of the surroundings
what are step down transformers used for in the national grid
decreasing the Potential Difference from transmission cables to mains supply in buildings so it is safe to use
what are step-up transformers used for in the national grid
increasing the Potential Difference from power station to transmission cables
what is the national grid
nationwide network of cables and transformers that link power stations to homes and offices
what is the function of the earth wire
safety wire to stop the appliance becoming live
what is the function of the neutral wire
completes the circuit
what colours are live, neutral and earth wires in the 3-core-cable
live=brown
neutral=blue
earth=green and yellow
frequency and voltage of mains electricity
frequency=50Hz
voltage=230V
what kind of current is supplied by mains electricity
alternating current (A.C.)
what is alternating current (A.C)
current repeatedly reverses direction
why is current provided by a cell called a direct current (D.C)
only flows in one direction
