Mains Electricity Flashcards
What are the 3 main wires in a Ring Main Circuit
- Live Wire
- Neutral Wire
- Earth Wire
What are the functions of the 3 main wires used in a plug
- Live Wire :
- This is the wire in which the electrical energy passes to the appliance - Neutral Wire:
- This wire completes the circuit - Earth Wire:
- The electricity will pass through this wire instead of going through the user, which prevents the user from getting shocked if there is a fault.
What are the different types of safety devices to protect you from an electrical shock
- Double Insulation
- Fuses
- Circuit Breakers
- Earthing
- Switches
How does a Fuse Work
The fuse contains a thin metal wire that has a low melting point.
Therefore, when the current becomes too big, the metal wire will melt.
This breaks the circuit and no current can flow through the circuit.
What are the advantages and disadvantages of using Circuit breakers instead of Fuses
Advantages:
+ No need to buy another circuit breaker after its used once, you will only need to turn on a switch.
+ Circuit breakers are faster to react than Fuses.
Disadvantages:
- They can sometimes be faulty because they contain moving parts that may be damaged. But Fuses do not contain any moving parts.
- The device is more expensive than a Fuse.
What is the use of an Earth Wire.
Many Electrical Appliances have metal casings. If a live wire touches this metal casing the casing can also become live and have current passing through it.
Therefore, if the user touches the casing, they will receive a severe electrical shock.
The earth wire is used to provide a low resistance path to earth for the current to travel in so that the current does not go through the human body, potentially electrocuting them.
What is double Insulation
This is a type of safety method where there are two layers of insulation.
This means that the user cannot get into contact with the Live wire, because the casing cannot become live as it is made from an insulating material instead of conductive material. Therefore, the device does not require an Earth Wire.
What is the heating effect of current
When current passes through wires that are used as heating elements in kettles, toasters, heaters and etc, the resistance of the wires is very high. This increase in resistance causes heat energy to be produced.
What is the equation for Power
Power = Voltage x Current
or
Power = Energy / Time
What is Power
This is the amount of energy that is transferred per second
What does the amount of electrical energy used by a device depend on
- The current
- The Voltage
- The amount of time the device is used for.
What is the equation for energy transferred
Energy transferred = Power x Time taken.
What is the difference between AC and DC current
AC current constantly changes direction going back and forth in the circuit.
DC current is constantly going the same direction in the circuit.
