Electric current does not flow on its own.
For current to flow in a circuit, a source of electrical energy is required.This source is called an electric cell.
Cells convert chemical energy into electrical energy and make current flow in a circuit.
Without cells, devices like torches, remote controls, mobile phones, and laptops cannot work.
Table of Contents
What Is an Electric Cell?
An electric cell is a device that produces electric current by chemical reactions.
It has:
- Two electrodes
- An electrolyte
When the circuit is completed, chemical reactions inside the cell push electric charges through the circuit.
Types of Electric Cells
Electric cells are broadly classified into two types:
- Primary cells
- Secondary cells
The main difference between them is whether they can be recharged or not.
Primary Cells
Primary cells are electric cells that cannot be recharged once their chemical energy is exhausted. After use, they must be discarded.
Construction of a Primary Cell
A primary cell generally consists of:
- Two different electrodes
- A chemical paste or liquid as electrolyte
Chemical reactions occur only in one direction.
Example: Dry Cell
The most common primary cell is the dry cell.
It is used in:
- Torches
- Wall clocks
- Remote controls
- Toys
Characteristics of Primary Cells
- Cannot be recharged
- Light in weight
- Easy to use
- Suitable for low current devices
Advantages of Primary Cells
- Simple construction
- Portable
- Cheap initially
Disadvantages of Primary Cells
- Cannot be reused
- Chemical waste causes pollution
- Costly in long run
Secondary Cells
Secondary cells are electric cells that can be recharged after use.
The chemical reaction inside a secondary cell is reversible.
Construction of a Secondary Cell
A secondary cell consists of:
- Two electrodes
- Electrolyte
During charging:
- Electrical energy is converted into chemical energy
During discharging:
- Chemical energy is converted into electrical energy
Example: Lead–Acid Cell
The most common secondary cell is the lead-acid cell.
It is used in:
- Car batteries
- Inverters
- Power backup systems
Other Examples of Secondary Cells
- Lithium-ion batteries
- Nickel-cadmium cells
These are widely used in modern electronic devices.
Characteristics of Secondary Cells
- Rechargeable
- Can supply large current
- Used for heavy-duty applications
Advantages of Secondary Cells
- Can be reused many times
- Economical in long run
- Less waste generation
Disadvantages of Secondary Cells
- Heavier
- More expensive initially
- Require careful handling
Comparison Between Primary and Secondary Cells
| Feature | Primary Cell | Secondary Cell |
| Rechargeable | No | Yes |
| Chemical reaction | Irreversible | Reversible |
| Usage | Low current devices | High current devices |
| Example | Dry cell | Lead–acid battery |
| Cost | Cheap initially | Cost-effective long term |
This comparison is frequently asked in exams
Importance of Cells in Daily Life
Electric cells:
- Provide portable power
- Store energy for later use
- Enable wireless devices
They are essential for modern technology.
Common Exam Traps to Avoid
- A battery is a combination of cells, not a single cell
- Primary cells cannot be recharged
- Secondary cells store energy chemically during charging
- Chemical energy → electrical energy, not the reverse
CELLS – FAQs
What is an electric cell?
A device that converts chemical energy into electrical energy.
What is the main difference between primary and secondary cells?
Primary cells cannot be recharged; secondary cells can.
Why are dry cells called primary cells?
Because they cannot be recharged.
Which cell is used in cars?
Lead–acid secondary cell.
Why are secondary cells preferred for heavy use?
They can supply large current and are rechargeable.
Is a battery the same as a cell?
No, a battery is a group of cells.
Which type of cell causes less waste?
Secondary cells.
Can primary cells be reused?
No.
What energy conversion occurs in a cell?
Chemical energy to electrical energy.
Why are lithium-ion batteries popular?
They are light and rechargeable.
Last-Moment Notes (Cheat Sheet)
CELLS
- Electric cell → chemical energy → electrical energy
- Cell provides potential difference
- Primary cell → not rechargeable
- Example → dry cell
- Secondary cell → rechargeable
- Example → lead–acid battery
- Primary cell reaction → irreversible
- Secondary cell reaction → reversible
- Battery → group of cells
- Primary cells → low current use
- Secondary cells → high current use
- Secondary cells economical in long run