Hydroelectric Power Generation

The question

How to approach this process diagram question

A process diagram shows how something is made or how a cycle works. Describe the stages in order, using sequence language and the passive voice.

1. Say what process the diagram shows and how many stages it has.
2. Overview: the number of stages, where it starts and ends, and whether it is a cycle or a straight line.
3. Describe every stage in order (First, Next, After that, Finally) mostly in the passive: the grain is crushed.
4. Do not add opinions or explain why; describe what happens.

How to plan this answer

Structure

1. Overview: the diagram shows six stages in one row, from the dam to the power lines, as a linear process with no return.
2. Body 1: stages 1 to 3, where water is held back by the dam, flows through a pipe and turns the turbine.
3. Body 2: stages 4 to 6, where the generator, transformer and power lines carry the electricity to users.

Key features to spot

• The dam holds back a large body of water, which is shown on the left of the diagram.
• The water flows through a large pipe down the hillside towards the power station.
• The force of the water turns the blades of the turbine.
• The generator converts the turning motion into electricity.
• The transformer changes the electricity, and power lines carry it to homes and businesses.

Useful vocabulary

• is held back by: The water is held back by the dam.
• flows through: The water flows through a large pipe.
• turns: The water turns the turbine.
• is converted into: The motion is converted into electricity.
• is transformed: The electricity is transformed before it is sent along the lines.
• is carried by: The electricity is carried by power lines.
• is followed by: The turbine is followed by the generator.
• the first stage: The first stage is the dam.
• the final stage: The final stage is the power lines.
• from left to right: The six stages are read from left to right.

Common mistakes

• Saying the dam itself generates electricity. The dam holds back water, and the generator produces the electricity.
• Presenting the process as a cycle. It is a one-way process ending with the power lines.
• Reversing the transformer and generator. The generator comes before the transformer.
• Describing the pipe as a tunnel. The diagram shows a pipe running down the slope.
• Using the active voice throughout. Use the passive where suitable, such as the water is directed.

Examiner tip: State in your overview that the process is linear with six stages from the dam to the power lines, then describe the water stages first and the electricity stages second.