Electricity - electricity in homes Flashcards
(38 cards)
what are the two types of current
alternating ( changes direction) and direct (one direction)
what type of current is in UK plug sockets
alternating
what is the frequency and voltage of UKs main electricity supply
50HZ 230V
examples of direct currents
batteries and cells
what colour is the live wire
brown
what are the three types of wires in appliances
live wire, neutral wire and earth wire
Describe the live wire
- carries 230V potential
- It provides the alternating voltage from the mains electricity supply.
- connected to a fuse in the plug
what colour is the neutral wire
blue
describe the neutral wire
- at or close to earths potential ( 0V )
- completes the circuit
- carries current away from appliance
what colour is the earth wire/ safety wire
green and yellow striped
describe the earth wire
- has 0V potential
- only carries current if there is a fault
- is a safety wire to stop the appliance from becoming live
energy transferred =
power x time
charge x potential difference
why will a 50W bulb use 50J of energy per second
because Joules are equal to watts
what is the national grid
the network of cables and transformers that connect power stations with houses and shops in the UK
What are power stations and what do they do
- buildings which create an electric current, which is an energy carrier
- Power stations produce electricity at a voltage of 25,000 Volts.
why are bigger power stations more efficient than smaller
- they can burn lots of fuel at high temperatures and this will create hot steam that’ll turn the turbines, and these are more efficient and higher temperatures
what do step up transformers do
increase voltage from 25,000 to 400,000V, causing the current to decrease.
This reduces the current and this reduces how much heat is lost when it’s being transported across the country.
This increases the efficiency of the National Grid system.
what do step down transformers do
To get electricity to a safer voltage (230 Volts) in our homes, step-down transformers reduce the voltage to a lower value.
what do fuses and circuit breakers do
protect us from electrical appliances by stopping the flow of electric current flow if it gets too high.
what are circuit breakers
- special devices that switch off the flow of current if the current is higher than a certain value.
- do the same job as fuses but can be used lots of times.
what are fuses
- contain a thin wire that melts if the current flowing through an appliance is too high.
This breaks the circuit and stops the flow of electric current. - can only be used once, must be replaced after
why are circuit breakers better than fuses
- circuit breakers break the circuit faster, reducing the risk of electric shock
- circuit breakers can be used more than once
what do fuse ratings do
they tell you the level where a fuse will begin to melt
how should you choose a fuse
The fuse chosen should have a value just above the normal current that an electrical appliance uses.
e.g - if the operating current is 3.9 A, and fuses with values of 3 A, 5 A or 13 A are available, the most suitable fuse is the 5 A fuse.
