understanding electric current
1. What is Electric Current?
Electric current is the flow of electric charge through a material.
In most circuits, the moving charges are electrons
Current flows only when there is a closed path (circuit)
Simple definition
👉 Electric current = flow of electrons
Unit of current
Measured in ampere (A)
1 ampere means a large number of electrons flowing every second
2. Why Do Metals Conduct Electricity?
Structure of metals
Metals have a special atomic structure:
Each metal atom has free (loosely bound) electrons
These electrons can move easily from atom to atom
What happens when voltage is applied?
A battery or cell creates an electric field
This field pushes free electrons
Electrons start moving → current flows
Why non-metals usually don’t conduct
Their electrons are tightly bound
No free electrons to move
So current cannot flow easily
3. What is a Cell and How Does It Produce Current?
An electric cell converts chemical energy into electrical energy.
Parts of a simple cell
Positive terminal (+)
Negative terminal (–)
Electrolyte (chemical inside)
What happens inside the cell?
Chemical reactions push electrons toward the negative terminal
Electrons want to move to the positive terminal
But they can only do this through an external circuit
4. How Current Flows in a Circuit
Step-by-step flow
Cell creates a potential difference (voltage)
Circuit is closed
Electrons flow:
From negative terminal
Through the wire and devices
To the positive terminal
⚠️ Note:
Electron flow: negative → positive
Conventional current (used in diagrams): positive → negative
5. How a Lamp Lights Up
Inside a lamp (bulb)
There is a thin wire called a filament
Usually made of tungsten (high resistance, high melting point)
What happens when current flows?
Electrons collide with atoms in the filament
These collisions produce heat
Filament becomes very hot
Hot filament glows → light is produced
Energy conversion
👉 Electrical energy → heat energy → light energy
6. Role of Current and Energy
Current
Controls how many electrons flow
More current → brighter lamp (up to a limit)
Energy
Supplied by the cell
Transferred to components (lamp, motor, heater)
Electrical power
Power tells how fast energy is used:
Power=Voltage × Current
7. Why a Lamp Does NOT Light in an Open Circuit
If:
Wire is broken
Switch is open
Cell is dead
Then:
No complete path
No electron flow
No current → no light