Q1.
Can we represent the circuits in a simpler manner?
Answer
Yes. Instead of drawing the cell, the bulb and the wires as pictures, we replace each component by an agreed symbol. A drawing of a circuit made with these symbols is called its circuit diagram.
| S.No. | Electrical component | How its symbol is drawn |
|---|---|---|
| 1. | Electric cell | One long line (+ terminal) and one short thick line (– terminal), side by side |
| 2. | Battery | Two or more cell symbols drawn in a row, long–short, long–short |
| 3. | Electric lamp | A circle with a cross inside it |
| 4. | Light Emitting Diode (LED) | A triangle touching a bar, with two small arrows pointing away to show that light is emitted |
| 5. | Switch in 'ON' position | Two small circles joined by a straight line |
| 6. | Switch in 'OFF' position | Two small circles with a line lifted away from one of them |
| 7. | Wire | A plain straight line |
Two things to remember while reading these symbols:
- In the cell symbol, the long line is the positive terminal and the short line is the negative terminal (Fig. 3.13a).
- In the LED symbol, the triangle points in the direction in which the current can flow, and the two arrows show that the LED emits light (Fig. 3.13b).
Why it happens: Symbols are quicker to draw, take less space, and mean the same thing to everyone. Bodies such as the IEC, ANSI and IEEE fix these standard symbols so that an engineer in Chennai and one in Canada read the same diagram in the same way.