9 September 2014

Electric Components : Science NCERT Notes

Circuit Diagram

A simplified conventional pictorial representation of an electrical circuit, using standard symbols for electric components, is called a circuit diagram. A ‘circuit diagram’ is also known as an electrical diagram, wiring diagram, elementary diagram or electronic schematic.

Electrical Circuit

A closed path formed by the interconnection of electrical components through which electric current flows is called an electrical circuit.
For a bulb to glow, it must be connected to battery rather than a cell, because a bulb will require more power. So if a circuit requires more power, then a battery should be connected.

Electric Components, NCERT Notes, CBSE Notes, Class 7

Cell Holder

A compartment that holds two or more cells together to form a battery is called a cell holder.

Open Circuit

If current does not flow through a circuit, then it is said to be an ‘open’ circuit or incomplete. Its switch is in ‘off’ position.

Closed Circuit

A circuit is said to be a closed circuit or complete when current flows through it.
Its switch is in ‘on’ position.


A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another. To identify the positive and negative terminals, they are denoted as + and –, respectively. These batteries are used in many devices, such as torch lights, mobile phones, calculators and even automobiles.


Different symbols are used to represent different components of electrical circuits, but the symbols used must be standardised. These symbols are easy to understand, remember and draw. 


It allows current to flow from one part of the circuit to another.


Switch On
When the switch is ON position, current will flow.
Switch Off
When the switch is in OFF position, current will not flow.


It supplies electric current. The positive terminal (+) of a cell is represented by a vertical long line, while the negative terminal (-) is shown as a parallel, shorter line.


The bulb glows if the switch is ON, and doesn’t glow if it is in OFF position.


It supplies electric current. A battery is a combination of two or more cells connected together.