Electricity Flashcards
What does 50 Hz mean
50 cycles per second, current changes direction 50 times
What do a.c and d.c stand for
Alternating current (direction of current changes) Direct current (direction of current remains the same)
Equations for frequency/time period
T= 1/F
TF=1
F= 1/T
Name the three wires in a plug and there colours
Earth wire- brown
Live wire- blue
Neutral wire- green/yellow
What’s does the earth wire do
Prevents the plug short circuiting and melting
Mains cable
Connects the plug to the mains and supplies electricity
Live wire
Active write connects fuse to mains
Fuse
Supplies a current
What are the three fuse sizes
3A, 5A and 13A
What wire attaches to the fuse
The live wire
What sort of the appliance is attached to the earth wire
The outer metal casing
What are the voltages of the wires
Live- 240 V
Neutral and earth- 0V
Where would the current travel if there was a fault with the live wire
Outer metal casing
What happens when too high a current flows through a wire and why
It would heat up and melt because the wire is not thick enough so the electrons collide a lot which converts kinetic energy into thermal energy
What equation links power, voltage and current
Current= power/voltage
Why does the Heating Element heat up when current flows through it
It has a high resistance so electrons struggle to through it at a high current because high resistance= low creepy so there are too many collisions and wire overheats and melts
What is 1kwh equal to
Energy used by 1000 W appliance in an hour
What’s the problem with a fuse which is too big
If the current increases due to a fault then this wouldn’t be detected until very high increase so could damage appliance
Circuit breaker
The break the circuit in the presence of a large current
Describe what how a circuit breaker works
Electromagnet gets stronger as the current increases so when it gets too strong the iron bolt is pulled out and the circuit is broken
How is a circuit breaker reset
The button is pressed which pushes the iron bolt back into place and always the iron bolt to fit back into it
