2 Mains electricity Flashcards
(38 cards)
What is an insulator?
A material through which it is very difficult or impossible for electricity to flow.
What is a conductor?
A material that allows electricity to flow through it easily.
What is a fuse?
The fuse is usually in the form of a cylinder or cartridge, which contains a thin piece of wire made from a metal that has a low melting point.
What is the circuit symbol for a fuse?
What happens if the current is too large in the circuit?
If there is too large a current in the circuit then the fuse wire becomes very hot and melts.
How does the fuse ‘blowing’ protect you?
Because the fuse has melted so the circuit is now incomplete, which prevents you from getting a shock and reduces the possibility of an electrical fire.
What must happen to the blown fuse?
It must be replaced with a new one of the same size before the appliance can be used again.
What is the correct fuse for a circuit?
The correct fuse for a circuit is the one that allows the correct current but blows if the current is a little larger.
What is the correct fuse if the current in a circuit is 2A?
3A
What is a circuit breaker?
Modern safety devices, such as those you might find in your consumer unit, are often in the form of trip switches or circuit breakers.
What happens if too large of a current flows into the circuit breaker?
A switch automatically opens making the circuit incomplete, so stopping any current from passing.
How does the switch then go back to normal after the fault in the circuit has been corrected?
The switch is reset, usually by pressing a reset button.
What happens to the switch or circuit breaker after the switch has been reset?
There is no need for the switch or circuit breaker to be replaced, as there is when fuses are used.
What should the earth wire be connected to?
To the appliances which have a metal casing.
What is an earth wire?
It is a copper wire coated in striped plastic that provides a path for current to flow from the case of the device to the ground
How does an earth wire protect the user?
If the live wire becomes damaged or breaks and comes into contact with the casing, the earth wire provides a low-resistance path for the current.
What would happen without the usage of an earth wire?
Anyone who touches the casing of the faulty appliance would receive a severe electric shock as the current passed through them to earth.
What is double insulation?
It is when some modern appliances now use casings made from an insulator such as plastic rather from metal. The user cannot touch the electrical parts since they are insulated in this way.
What kind of wire do appliances use that have double insulation?
They use a two-wire flex.
What is a flex?
It is a wire.
Do doubly-insulated appliances need an earth wire?
No this is because the double-insulation protects the user of the appliance from an electrical shock by preventing any possibility of the external casing becoming live (the live wire can not touch the casing even if wires inside become loose), thus eliminating the need for an earth connection.
Where should switches in main circuits be placed?
In the live wire so that when the switch is open no electrical energy can reach an appliance.
What happens if the switch is placed in the neutral wire?
Electrical energy can still enter a faulty appliance, and could possibly cause an electric shock.
How is the wiring in a house designed?
The wiring in a house is designed to let current pass through it easily.
