Electricity in the home

Electricity

What is AC?

Alternating current

What is alternating current?

Constantly changing direction.

What is the potential difference of UK mains supply?

230 V

What is the frequency of UK mains supply?

50 Hz

What is DC?

direct current

What is direct current?

Only flows in one direction

What produces a direct current?

Batteries or cells.

What type of current is mains electricity?

Alternating current

Benefit of alternating current

Easy to use a transformer to increase of decrease the potential difference.

What can show the pattern of electrical current?

Oscilloscopes

What does an alternating current look like?

A transverse wave. Has peaks and troughs.

What does the height of peak tell us?

The maximum potential difference

What does a direct current look like?

A straight line

What does time from one peak to the next show us?

One complete cycle

How to calculate frequency of alternating current?

1/time for one cycle

What are three core cables made of?

Copper, as it is a good conductor of electricity.

What are the coatings of cables made of and why?

Made of plastic which does not conduct electricity.

What colour is the live wire?

Brown

What does the live wire do?

Carries the potential difference from supply.

What is the live wire connected to?

The fuse

What is the symbol for a fuse?

A rectangle with a horizontal line through the middle.

What colour is the neutral wire?

Blue

What does the neutral wire do?

Complete the circuit.

What is the potential difference of the neutral wire?

0V

What colour is the earth wire?

Green and yellow stripes

What is the earth wire?

A safety wire to stop appliance from becoming live.

How dangerous is the live wire?

Extremely dangerous and could be fatal if touched.

What is the potential difference of the earth?

0V

What would happen if someone touched a live wire?

A current would flow through them into the Earth and the person would be electrocuted.

Why are appliances with a metal case dangerous?

If live wire becomes loose and touches metal case, it will become live.

This could give someone a fatal electric shock if they touch the metal case.

What is attached to the metal case?

The earth wire which is connected to a metal rod in the ground.

What happens if the case becomes live?

A huge current flows to Earth, the fuse melts and shuts off the current.

What does energy transferred depend on?

How long the appliance is left on for and its power

Equations for energy transferred

E = power x time

E = charge flow x potential difference

What are the power equations?

P = VI

P = I²R

What is the national grid?

A system of cables and transformers

What does the national grid to?

Transfer electrical power from the power station to where it is needed

What are power stations able to do?

Change amount of electricity produced to meet demands.

e.g more energy may be needed in evenings when people come home from work or school.

How is this made efficient?

Electricity is transferred at a low current, but a high voltage, so less energy is lost as it travels through cables.

Step - up transformers

Increase the voltage as the electricity flows through the cables

Step - down transformers

Decrease the potential difference flowing through cables to make it safe.