Electricity in the Home Flashcards
What is our electrical supply at home?
240 Volt, 50 Hertz, a.c. supply
What is an a.c. supply?
The current is continually changing direction in the live and neutral wires, and the 50 hertz tells us that this is happening 50 times per second. Has a live and neutral terminal.
What is d.c. supply
Type of current met when using batteries. The conventional current always flows in one direction from positive to negative. Has a positive and negative terminal.
Where is the fuse placed in a a.c. supply?
Between the switch and live wire. (Switch is always placed in the live wire or positive wire)
Why are fuses included in an electric circuit?
As a protection device. They prevent current that are too large flowing in the circuit and are always connected to the live wire so that should they melt and blow, the appliance does not remain live. They have a wire inside that melts and breaks the circuit when the current becomes too large. Protects against internal damage and fire risk.
What to note about a fused plug?
Blue goes left
Brown goes right
Function of live and neutral wires?
These carry out the current (surges) to and from the appliance. There are equal but opposite currents in these wires
Function of the earth wire?
Appliances with metal casings mush have an earth wire. It is connected to the inside of the casing. If the live wire accidentally touch’s the casing the user could be electrocuted if they touch the machine. To prevent this the earth wire provides an alternative route for the current. The resistance is low so the current is high, this melts the fuse and disconnects the live voltage supply
What is double insulation?
Some electrical appliances have an outer case made from an insulating material such as plastic. The user could never get a shock from such items and it is therefore pointless to make an earth connection
What is a unit of electricity?
Kilowatt-hour (kWh). 1 kWh is the energy used when a 1kW appliance is used for 1 hour.
How to calculate total cost of electricity at home?
Cost per unit X Number of units
How to calculate cost if power rating is known?
Power in kW X Time in hours X Unit cost
