10 January 2014

Electricity And Circuits

An electric cell provides electricity to various devices that are not directly fed by the supply of electricity.

Electric Cell

An electric cell  consists of two terminals.  One is a positive terminal and the other one is a negative terminal.  A chemical that helps produce electricity to connected devices.


A bulb consists two terminals. 
filament is a spirally wound wire inside the bulb supported by two thick wires at its ends. An electrical cell is connected to the terminals of a bulb so that electricity from the cell can pass through the bulb. This electricity makes the filament in the bulb glow and emit light.

Electrical circuit:

Electricity needs a path to pass from the positive terminal to the negative terminal of an electric cell.  A connection that provides a path outside an electric cell, for the electricity to pass from the positive terminal to the negative terminal of the cell, is called an electrical circuit.    
For example, a bulb glows only when the positive terminal and the negative terminal of an electric cell are connected to the two terminals of the bulb.
If the wires from the bulb are connected to the same terminal (either positive or negative), then the bulb doesn't glow.
Sometimes, the bulb may not glow even though the connections are properly made.
This is because the flow of electricity is incomplete as the filament in the bulb is broken. A broken filament bulb is said to be fused.


A device that is used to stop the flow of electricity by breaking the circuit is called a switch. Switches have wide range of applications. Some common types are:
  • Toggle switches, which are used in our houses.
  • Pushbutton switches, which are used in the starter of a water pump.
  • Joystick switches, which are used in the remote control unit of a toy car

Electric Conductors and Insulators:

All materials do not allow electricity to pass through them. Materials that allow electricity to pass through them are called conductors. Conductors conduct electric current. Since metals are good conductors of electricity, electric wires are made of metals. These electric wires act as conducting materials. So they are used to make electrical circuits. Some common conductors that conduct electric current are copper, silver, gold and aluminium. Copper is the most popular material used for wires.   Sometimes we receive electric shocks because our bodies are also good conductors of electricity.
Materials that do not allow electricity to pass through them are called insulators. Insulators oppose electric current and so they are used as protection from the dangerous effects of   electricity. Some common insulators are glass, air, plastic, cotton, thermocol, wood and rubber.
Water is a good conductor of electricity, but in its purest form, called distilled water, it acts as an insulator. Distilled water is, therefore, used in batteries as an insulator.
We use various electrical appliances every day. Without the help of insulators, the use of electrical appliances is impossible. The parts of the electric appliances that we touch are covered with insulating material. For example, plugs and switches are covered with an insulating material such as plastic, and the wire attached to the plug is a metal wire, which is a conductor. So conductors and insulators work hand in hand.

With our free PDF notes you can get success in any competitive or entrance exams like CTET,  KVS, NET, CAT, MAT, CMAT, SSC, B.ED, IBPS Recruitment, IAS, CSAT, State Civil Services Exams, UPTET, PSTET, HTET & many more. It also provides NCERT solutions, CBSE, NTSE, Olympiad study material, Indian General Knowledge, English, Hindi, Mathematics, Current affairs, Science, S.ST, model test papers, important Questions and Answers asked in CBSE examinations.