September 21, 2021

Electric Circuit

A closed path for the flow of electricity is called an electric circuit. The circuit consists of a voltage, switch, resistor and a conductive path.

Electric cell

The main component of an electric circuit is a cell or a battery which gives power to the circuit. The capacity of a single electric cell is 1.5 volts. The positive and negative terminals are the two major parts of a cell. The positive terminal has a cap and the negative terminal has a disc. The two terminals of the cell are joined by electric wires containing a torch bulb and switch. If two or more cells are joined together, they form a battery. An electric cell used in a torch is called a dry cell. 

Torch bulb

The small electric bulb that produces light when a torch is switched on is called a torch bulb. The small glass bulb fixed on a metal case is the major component of the torch bulb. Inside the bulb there are thin wires and thick wires. The thin wire inside the body is called the filament of the bulb, which is made up of tungsten. The glowing of the filament occurs when the current is passed through the circuit. One of the thick wires is connected to the metal tip of the bulb whereas the other thick wire is connected to the metal case of the bulb. The metal tip at the base of the bulb and metal case of the bulb are the two terminals of the torch bulb.

Working of torch bulb

When the two terminals of the cell are connected to the two terminals of the torch bulb, the electric current passes through the filament and it glows. If the cell is weak or when the cell is connected to the bulb with loose wires, the bulb does not glow. Even when the bulb is firmly connected to the cell by wires without any gap, the bulb fails to glow. This is because the bulb has got fused. When the filament of the bulb gets broken, the bulb is said to be fused.


LED is a standard source of light in many of the  light emitting electronic appliances. LEDs have a positive terminal and negative terminal. The positive terminal is also called the anode and the negative terminal is also called the cathode. Since cathode has a flat spot, it can be easily differentiated from anode. 


Switch is a simple device that is used to either break the electric circuit or to complete the circuit. It works by opening or closing the gap in the circuit. When the switch is in off position, the gap opens up in the electric circuit and the flow of electricity is broken. When the switch is in on position, a complete circuit is made. This does not interrupt the flow of electricity. The purpose of a switch is to turn off and on the appliance by opening or  closing the circuit.

Making a circuit

Every cell has a positive and negative terminal to which the conducting wires are connected. The positive terminal of the cell is connected to the switch with a wire. Another wire connects the other end of the switch to one side of the bulb holder. The negative terminal of the cell is connected to the other end of the bulb holder with a connecting wire.  

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