Mains Electricity Flashcards
What are some electrical insulators?
Plastic and rubber
What are some electrical conductors?
Metals - copper and silver
What is double insulation?
Is when an appliance has plastic casing and no metal parts are showing
Unit for current
Ampere (A)
Unit for electrical charge
Coulomb (C)
Unit for energy
Joules (J)
Unit for resistance
Ohms (Ω)
Unit for time
Seconds (s)
Unit for voltage
Volts (V)
Unit of power
Watt (W)
How does double insulation help?
Plastic is an insulator so it stops a current flowing - can’t get an electric shock
What is an insulator?
A material that stops current running through it
What is a conductor?
A material that allows current to flow through it
What are three wires in a plug called and what colour are they?
Live wire - Brown
Earth wire - Green and yellow
Neutral wire - Blue
What does the live wire do?
It alternates between high and low voltage around 230V
What does the neutral wire do?
It stays at 0V
What does the earth wire do?
It’s for safety and works together with the fuse
What and why do appliances with metal casing need?
It must be “earthed”, this reduces the danger of electric shock and can’t become live
What happens when a fault occurs in an appliance with a metal case?
A big current flows through the live wire, case and earth wire
This surge blows/melts the fuse which stops the live supply
This isolates the whole appliance
What does a fuse prevent?
It makes it impossible for an electric shock and stops fire from the heating of a large current
What are advantages of electrical insulation?
It lowers your heating and coding costs
What is a circuit breaker?
Similar to fuses but it opens a switch when there’s a surge of current
How is a circuit breaker more convient than a fuse?
A circuit break can be reset by flicking the switch. A fuse has to be replaced once melted
What’s an example of a circuit breaker?
RCCB
How does a resistor heat up?
When there’s an electric current in a resistor there’s an energy transfer which heats it up
What happens if someone touches the live wire with a RCCB?
The current will flow through them into the earth. The neutral wire will carry less current than the live wire and the difference will be detected by the RCCB.
Why is an RCCB better than a fuse?
It operates faster. They break the circuit when there’s a current surge but the fuse stops when it melts.
Why does the resistor heat up (electrons)?
Because electrons collide with ions in the lattice which makes up the resistor as they flow through it. The ions gain energy which makes them vibrate and heat up.
How does the heating effect the resistors performance?
This increases the resistors resistance - less current will flow
How can the heating of resistors be used in appliances?
Toasters - high resistance coil of wire, when current passes temp increases and glows (infra-red)cooking the bread
What is the calculation for power (P)?
Power = Current x Voltage
P = I x V
What is the calculation for energy transferred? (E)
Energy transferred = current x voltage x time
E = I x V x t
What is DC?
Direct current - Current only travels in one direction
What has a DC output?
Batteries
What is AC?
Alternating current - The current direction reverses half cycle.
What has an AC output?
“Mains” power
