Electricity in the home Flashcards
What is the National grid?
It is a network of cables, pylons and transformers.
What is the function of the National grid?
Its function is to deliver electricity to homes, schools, offices and factories.
How does the National grid do its function?
It does this in the most efficient way possible, that is by reducing the energy loss across cables as heat.
What does a step up transformer do?
Increases the p.d, but decreases the current; a lower current reduces heat loss.
What is the equation for power loss?
P = I^2R
Power (Watts) = Current^2 (Amps) x Resistance (Ohms)
What does the live wire do?
What colour is the live wire in a mains plug?
The electricity goes in and is transferred from the power station to the user.
Brown
What does the neutral wire do?
What colour is the neutral wire in a mains plug?
The electricity goes out and is transferred from the user to the power station.
Blue
Where does the earth wire go?
What colour is the earth wire in a mains plug?
It goes into the ground through a large conductive hole.
Yellow and green
Why are most of the plug and cable externally made from plastic?
For their insulation properties.
The brass pins connected to the plug are…
good conductors and are strong, resilient and rust resistant.
Inside the plug how does electricity flow through it?
electricity enters via the pin connected to the brown wire, and then onto the appliance. Then it is connected to the blue as the output back to the socket.
What does the Earth ensure if a live connection at the appliance touches the metal casing?
There is a surge of current that can be transferred away. (Assuming the fuse doesn’t blow first).
What is the equation for Power in terms of energy and time?
P = E / t
P = E / t rearranged is E = Pt and this expression is used to determine?
the energy used by an appliance in a specific time. E.g. A filament lamp (100W) is switched on for 30 minutes. How much energy will it use?
What is the equation for efficiency?
Efficiency = useful energy/power output / total energy input (x100)