Unit 4- Mains Electricity Flashcards
What does the brown wire do
Delivers the energy to the thing it is powering
What does the blue wire do
The blue wire takes the electrons away with no energy
What does the earth wire do
99.9% of the time it is pointless. But that 0.1% of the time it is used when the power station sends to much energy and the yellow and green wire takes the energy in the ground and absorbs it. The earth wire is just a safety feather
What is the danger of spilt drink on heater
It is an electrical conductor, it will start a fire or electrocute you (connects the person to the electricity)
What is the danger of lots of plugs in a sockets
Overheats which leads to fire (overload)
What is the danger of pulled wire
Could damage the connection inside the wire
What is the danger of frayed cable
You are exposing the wire, you could get electrocuted
What is the danger of pushing metal objects into electrical socket
You could get electrocuted
What is the danger of long cable
It is a trip hazard
High energy transfer=
High power
What does current cause
Heat in the wires and components
What is needed when heat is produced
More voltage is needed to transfer energy to the components
Power (P) =
Current (I) ❌ voltage (V)
What is power measured in
Watts
What is current measures in
Amps
What is voltage measured in
Volts
Energy (E) =
Power (P) ❌ Time (T) or current (I) ❌ voltage (V) ❌ time (T)
What is energy measured in
Joules
What power measured in
Watts
What is time measured in
Seconds
What are the three different colour wires in a plug and what are they all called
Blue: neutral
Brown: live
Green/ yellow: Earth
What is the job of the fuse
Protects circuit from damage if current is high or if it has overheated
How does the fuse protect the circuit from damage
Thin fuse wire melts ➡️ break in the circuit
Can you reset the fuse
No, need to replace the fuse
It the fuse effective
It is slow, circuit breaks slowly
What is the job of the RCCB
Protects circuit from damage if current is high or if it has overheated
How does the RCCB protect the circuit from damage
Switch open ➡️ breaks circuit
Can you reset the RCCB
Yes, you have to close it
Is the RCCB effective
It is fast, the circuit breaks instantly
Voltage variation of the line terminal
The voltage of the live terminal varies sinusoidally between +325 and -325 taking 1/50 or 0.02 second to complete one cycle
What are the danger of mains electricity
- Fire :
This can be caused by too high current flowing along cables or through appliances
A fuse or circuit breaker is used to limit the current to a safe level - Electrocution :
This can occur when contact is made with the live wire. Death can occur if a current above 100ma (0.1A) flows through the body
The earth wire in combination with a fuse or circuit breaker can prevent electrocution
What is a fuse?
A fuse is a length of wire designed to melt and so breaking a circuit when the current passes through it goes above a certain level.
The fuse rating must be slightly higher than the normal current so it melts in a surge and protects from shock.
