P5 Flashcards
how does direct current flow
In one direction only
How does alternating current flow?
It repeatedly changes direction
Which two wires does a mains circuit have?
A live wire and a neutral wire
Where is the electricity that flows to your house supplied from
From powerstations through the national grid
What is the national grid?
A network of cables and transformers
What are step up transformers used for?
To transfer electricity to the national grid.
What do step up transformers do?
They make the size of the alternating potential difference much bigger
What are step down transformers used for?
To supply electricity from the national grid to consumers
What is the peak potential difference of an ac supply?
The maximum voltage measured from zero volts
Where is the earth wire connected to in your home?
The ground
What are the cases on plugs made from?
Stiff plastic
Why is the case made from plastic?
Because plastic is a good insulator
What colour is the live wire?
Brown
What colour is the neutral wire?
Blue
What colour is the live wire?
Green and yellow stripes
What are the cables used for mains appliances made up of
2 or three insulated copper wires surrounded by and outer layer of flexible plastic material
Is the mains wire connected to the longest or shortest pin in the plug?
The longest
What is the equation to calculate power
Power (Watts) = energy transferred (Joules) / time (seconds)
What is the formula to find the power supplied?
power supplied (Watts) = Current (Ampres) X Potential difference (Volts)
What are the fuses that domestic appliances are often fitted with
3A , 5A or 13A
What is the formula to find the correct rating for a fuse?
Electrical power ( Watts) / Potential difference ( Volts)
What is the formula for charge flow?
Charge flow = Current (ampres) X time (Seconds)
What is the formula for efficiency?
Output power / input power X 100
