Electrcity Flashcards
How many watts are in a megawatt
one million watts
how many watts are in a gigawatt
One billion watts
from what end of the cell does current flow from
negative (to positive)
The current ina series circuit is _____
the same
The current in a parallel circuit _____ to the total ____ ________ ____ ______
the current in parallel circuit sums to the total current leaving the cell
3 stages of the national grid
step-up transformer, high voltage cables, step down transformer
How does the national grid work?
Electricity passes through step up transformers which increase the potential difference to several hundred volts.
Electricity then passes through high voltage cables but cannot be passed onto homes yet as potential different would be far too high
Electricity passes through the step-down transformers which redue the potential difference to 230V
DC
direct current
AC
alternating current
What is DC
electrons only travel in one direction
What is AC
electrons that are constantly changing direction
Benefit of AC?
Very easy to use a transformer to increase or decrease the potential difference
Frequency of AC in the UK
50 hz
potential difference of AC in the UK?
230 voltage
Potentiall difference does/does not change in DC
does NOT
What is the wire + casing made of in the 3 core cable?
wire = copper
casing = plastic
What is the brown wire?
Live wire
What is the purpose of the live wire?
Carries alternating potential difference from the supply (230V) connected to a fuse in the plug
What is the Blue wire?
Neutral wire
What is the purpose of the neutral wire?
completes circuit, potential difference = 0V
What is the green/yellow wire?
Earth wire
What is the purpose of the earth wire
safety wire to stop appliance from becoming live (having voltage)
Why are appliances with metal casings dangerous?
If the live wire becomes loose, the metal casing could become live too, and if someone were to touch the live metal casing they would be elctrocuted and die
How does the earth wire solve the porblem of live wires and metal casings?
Earth wire is attatched to metal case and ground so if the case becomes live, the current flows to the earth
