AQA GCSE Physics - Revision national grid

What is the national grid?

A network of transformers, power stations and cables

What does the national grid do?

Supply homes with electricity

What do transformers change?

Voltage and current

What change of the national grid is brought about by a transformer and makes the system more efficient?

A change in voltage

Increasing the voltage will _____ the current

Decrease

High current in a pylon wire means there is a _____ amount of heat loss

High

Maximum efficiency in the national grid is a _____ current and a _____ voltage

Low, high

What are the types of transformer on the national grid?

Step-up and step-down

A step up transformer _____ the current and _____ the voltage

Decreases, increases

A step down transformer _____ the current and _____ the voltage

Increases, decreases

Where on the grid would you find a step up transformer?

Between the power station and the pylons

Where on the grid would you find a step down transformer?

Between the pylons and the home

What is the purpose of a step down transformer?

Makes the electricity safe for use in the home

What are the advantages of pylons?

Cheap to build and easy to repair

What are the disadvantages of pylons?

Ruin landscape, some people think they affect health

What are the advantages of below ground cables?

Don't spoil the landscape, no health affects

What are the disadvantages of below ground cables?

Expensive to build, hard to repair, hard to cross roads and rivers

Why are fuels with a short start up time needed?

As demand for electricity varies throughout the day

Which fossil fuel has the lowest startup time?

Gas

What is the problem with all sources of renewable energy except hydroelectric?

It cannot be switched on and off to meet demand

Which two methods of energy generation are left to run all the time?

Coal and nuclear

What is the method of storing electricity for the national grid?

Pumped storage systems

What is a the pumped storage not able to be?

100% efficent