Mains Electricity Flashcards
What is direct current (d.c.)
cells and batteries supply current that always passes in the same direction
this is called d.c.
What is alternating current?
an alternating current (a.c.) is one that is constantly changing direction
What are the properties of mains supply?
it is an a.c. supply
in the UK it has a frequency of 50 hertz and is about 230 V
What are the features of a plug?
case made from tough plastic because they are good insulators
three pins are made from brass which is a good conductor
there is a fuse between the live terminal and live pin, which breaks when the current exceeds the fuse rating
What are the names of the different and what is there location in the plug?
bLue - neutral - Left of plug
bRown - live - Right
sTriped - earth - Top
What are RCCBs?
some circuits are protected by Residual Current Circuit Breakers
they detect a difference in current between the live and neutral wires
it works much quicker than a fuse
Why are earth wire used?
metal cased appliances are earthed to prevent a current flowing on the case
some appliances are double insulated and don’t require a earth cable
What happens to a resistor with a charge flowing through it and how do filament bulbs waste energy?
resistors get hot
a lot of energy is wasted as heat in filament bulbs
less energy is wasted in power saving lamps such as Compact Fluorescent Lamps
