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Drawing circuits


 

Symbols are used in drawing circuits instead of drawing pictures. It is complicated and confusing to draw pictures to show someone, how a circuit is connected up. Also, it is time consuming. So, we use circuit symbols to draw circuits in order to overcome these problems. In this lesson you’ll be able to know some of the circuit symbols that we use in drawing circuits.

 

What is a symbol?

A symbol is a sign, letter or diagram that represents or stands for something. For example in circuit drawing we use many symbols. To show a bulb or lamp we use following symbol;

lamp-bulb

Example of circuit symbol lamp or bulb

 

 

What are the advantages of using symbols in drawing circuits?

 

1) It saves time.

2) It is a good way of showing someone how a circuit should be connected up.

 

wire-symbol lamp-bulb cell-symbol diode-symbol
battery-symbol ammeter-symbol voltmeter-symbol buzzer-symbol
fuse-symbol IDR-symbol motor-symbol resistor-symbol
variable-resistor-symbol switch-closed switch-open-symbol thermistor-symbol

Examples of circuit symbols used in drawing circuits

 

Examples of drawings of a simple circuit with a bulb, cell and the switch

simple-circuit-switch on

Example of a simple circuit with the switch ON

 

simple-circuit-switch off

Example of a simple circuit with the switch OFF

 

circuit-with-two-bulbs

Example of a simple circuit with two bulbs with the switch ON

 

Look at each circuit diagram below. Which one do you think the bulb or bulbs will light.

 

circuit-diagram

 

 

Terminals of a cell

 

What is a terminal of a cell?

One of the ends of a cell to which the wires must be connected in a circuit is called a terminal of a cell.

 

How many terminals are there in a cell?

Two

 

What are the two terminals in a cell?

 

1)     Negative terminal (-)

2)     Positive terminal (+)

 

How does the electricity flow between these two terminals of a cell?

Electricity flows from the negative terminal (-) to the positive terminal (+) of the cell.

 

If you have got only a cell and a bulb, will you be able to light the cell?

No.

Why? Because, first we must join the two terminals of a cell by a material that conducts electricity.

Drawing circuits - battery

Example of a battery
A battery gives power to the circuit. As shown in the picture it has two terminals.

 

Positive and Negative Terminals of a cell

 

What are the materials that conduct electricity?

 

1)     Wires

2)     Metal

 

What is the positive terminal on a circuit diagram?

The long vertical line

 

What is the negative terminal on a circuit diagram?

The short vertical line

 

terminals

Symbolic representation of Terminals of a cell