Domestic Uses Of Electricity Flashcards
A direct current (d.c.) supply:
- has a direct potential difference, current direction is constant
- used in cells and batteries
An alternating current (a.c.) supply:
- has an alternating Potential difference, current direction alternate
- used in mains electricity
What is the mains electricity and direction in UK
230V
Direction- 50 times a second, i.e. it has a frequency of 50Hz
What is the electrical potential of the live wire
BROWN
-230V Potential
What is the electrical potential of the neural wire
BLUE
-at or close to 0V earth potential
What is the electrical potential of the earth wire
GREEN AND YELLOW STRIPES
-0V potential
During operation:
- potential difference causes current to flow through live and neutral wires
- live wires carries alternating potential from supply
- neutral wire completes circuit
- current will only flow in the earth where if there is a fault connecting it to a non-zero potential
The earth wire is a ______ wire
SAFETY, stops exterior of an appliance becoming live
What happens if you touch a live wire
- creates a large potential difference across body and results in a large current flowing through body
- can be dangerous even if a switch in circuit is open
A television might be switched off (so no current flows) but sill plugged in and switched on at the wall:
- live wire between wall and switch on the TV is still at an alternating potential
- all it needs is a path for electricity to flow through
- this path could be a damaged cable exposing live wire
- if someone touches it, they will get an electric shock
Equation for power
Energy transferred
—————————-
Time
Work done
——————-
Time
Equation for efficiency
Useful energy output
——————————-
Total energy input
HT, to increase the efficiency of an energy transfer…..
The amount of wasted energy needs to be reduced
