This is a Clilstore unit. You can link all words to dictionaries.


Basic electronic components. Relays



In this lesson we are going to learn what a relay is, how it works and its applications.

If we want to control much more powerful outputs such as large lamps or motors we can use a relay.

A relay is just a type of switch, except that the position of the switch (on or off) is controlled by an electromagnet. When a coil is connected to a power supply it makes it work like a magnet. This magnetic force allows the contacts of the switch to be pulled together.


Relay symbol


This image shows how our real relay corresponds to the schematic diagram symbol for a relay.

The coil is attached to the bottom two lugs.

The lug in the centre of the picture is "common".

The upper lug is "normally closed".

The one below it is "normally open".   



Activity 1. Speaking.

Select each word in bold in the text above, go to Multidict and choose the dictionary called WordReference. Listen to the sound of the word and say it aloud. Repeat each word 5 times.


Activity 2. How a relay works.

Click on the Video button and watch the video twice. The first time without transcription. You can use Multidict if you need it.



After this, you can answer the following questions:

How many circuits has a relay?

What are the names of the contacts?

When can we use a relay?

and share your responses with the rest of the class.


Activity 2. Different uses of relays.

 Click on the Practice button and do the exercises.


Now we are going to find out about another electronic component.

Click on the Lesson 4 button to find out about transistors.

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