We use electric lamps every day in our homes, classrooms, and streets. But have you ever wondered how a bulb glows?
A bulb glows only when electric current flows through it. For electric current to flow, we need a complete circuit made with the correct electrical components.
Without a complete circuit, the bulb will not glow.
What is an Electric Circuit?
An electric circuit is a closed path through which electric current flows from the source, through different components, and back to the source.
It is like a road for electricity to travel.
If the road is broken anywhere, electricity cannot move.
Components Needed for a Simple Circuit
To make a lamp glow, we need four main parts:
a) Cell / Battery
- A cell is the source of electrical energy.
- It stores chemical energy and converts it into electrical energy.
- A battery is made of two or more cells joined together.
Function:
Supplies electrical energy to the circuit.
b) Connecting Wires
- Wires are usually made of copper or aluminium.
- They allow electric current to move from one component to another.
Function:
Connect all parts and carry electric current.
c) Electric Lamp / Bulb
- A bulb gives light when electric current passes through it.
- In a filament bulb, the filament becomes hot and glows.
- In an LED lamp, light is produced by semiconductor materials.
Function:
Converts electrical energy into light energy.
d) Switch
- A switch is used to open or close the circuit.
Function:
Controls the flow of electric current.
- Switch ON → circuit closed → bulb glows
- Switch OFF → circuit open → bulb does not glow
What is a Complete Circuit?
A complete circuit means all components are properly connected in a closed loop with no gaps.
Current flows in this path:
Battery → Wire → Bulb → Wire → Switch → Back to Battery
When current passes through the bulb, it glows.
Complete circuit
What is an Incomplete Circuit?
An incomplete circuit has a break or gap in the path.
Examples:
- Switch OFF
- Broken wire
- Loose connection
- Dead battery
- Missing component
When the path is broken, current cannot flow, so the bulb does not glow.
An incomplete circuit
How Does the Bulb Glow?
When the switch is ON:
- The battery supplies electrical energy.
- Current flows through the wires.
- Current passes through the bulb filament or LED.
- The bulb converts electrical energy into light.
So the bulb glows.