electricity (mains) Flashcards
(26 cards)
What is AC?
Alternating current: Charge moves backwards and forwards at a certain frequency such as mains electricity and generators
What is DC?
Direct current: Travels in one direction such as cells and batteries
What is the potential difference in AC?
It changes direction due to potential of the live wire changes between positive and negative while the neutral wire remains at zero volts.
What is the potential difference in DC?
It always stays the same
What current supply is UK mains electricity?
AC
What is the frequency of UK mains electricity?
50Hz
What is the potential difference of UK mains electricity?
230v
What is the live wire in a plug?
The brown wire which carries AC current to the device
What is the neutral wire in a plug?
The blue wire which connects to the mains supply and completes the circuit
Which is the earth wire in a plug?
The yellow and green wire which provides a path to the ground in case of a fault
How do fuses stop danger in a fault?
It is between the live wire and live pin and melts when current is too high
How does earthing stop danger in a fault?
A large current flows from the live wire to the earth and melts the fuse
What is double insulation?
An appliance with a casing made of an insulating material and have no earth connection
How do electric shocks occur?
The live wire has a potential of 230v and the ground has a potential of 0v creating a potential difference
What is power?
The rate at which energy is transferred in circuits
What is power measured in?
Watts (W)
What is energy generally measured in?
Joules (J)
What is energy in appliances measured in?
Kilowatt hours (kWh)
What is the national grid?
A series of cables and transformers that transport current across the country
Why does the national grid use low current?
So that it is not lost through heat
What do step up transformers do?
They increase the potential difference 275,000 v and decreases the current
What do step down transformers do?
They decrease the potential difference to 230 v to make it safer for homes and increases the current
How does static charge occur?
Certain materials are rubbed together and become electrically charged. Negatively charged electrons are rubbed from one material to another. The material that gains electrons becomes negatively charged and the material that loses electrons becomes positively charged.
How does sparking occur?
When two charged objects interact, it sparks. This is the sudden flow of electric current across the gap between the objects which heats the air enough for it to glow.
