⚡ 1. What is Electricity?
Electricity is a form of energy that powers our lights, fans, TVs, phones, and almost everything around us.
It is caused by the flow of tiny particles called electrons. When electrons move through a
material, we get electric current.
Electric current = the flow of electric charges (electrons) through a conductor
The path through which current flows is called an electric circuit.
🔋 2. The Electric Cell (Battery)
An electric cell is a device that converts chemical energy into
electrical energy. It provides the "push" (voltage) that forces electrons to move through the
circuit.
- A cell has two terminals: positive terminal (+) and negative terminal
(−)
- The positive terminal is usually the cap/bump on one end; the negative terminal is the flat base
- Current flows from the positive terminal, through the external circuit, to the negative
terminal
- Multiple cells connected together = a battery
- Common types: Dry cell (torch battery), button cell (watch), lead-acid battery (car)
📸 Image Prompt
A labeled diagram of a AA dry cell battery: Cylindrical shape, the positive
terminal (small metal bump/cap) labeled "+ve Terminal" on the top, and the flat negative terminal
labeled "−ve Terminal" at the bottom. A simple circuit diagram alongside showing a cell symbol (two
lines — one long thin and one short thick), connected to a light bulb symbol and a switch, with arrows
showing current flow direction from + to −. Clean white background, educational style, colorful labels.
Fig. 12.1 — Parts of an electric cell and its circuit symbol
💡 3. Electric Circuit — How Electricity Flows
An electric circuit is a complete, closed pathway through which electric
current can flow. If the circuit is broken/incomplete at any point, current STOPS flowing and the device
stops working.
Essential Parts of a Simple Circuit:
- Electric cell/battery — provides the electrical energy (like a pump)
- Wires (conductors) — provide the path for current to flow
- Bulb/Device — uses the electrical energy
- Switch — opens (breaks) or closes (completes) the circuit
OPEN circuit: The switch is OFF — circuit is broken — current does NOT flow — bulb does NOT
light up.
CLOSED circuit: The switch is ON — circuit is complete — current flows — bulb LIGHTS UP.
📸 Image Prompt
Two circuit diagrams side by side: Left diagram labeled "Open Circuit (Switch OFF)"
— shows a battery (+ and - labeled), two connecting wires, a closed switch symbol shown as OPEN (gap in
the line), and a light bulb symbol (circle with X inside) — the bulb shown as unlit (grey). Right
diagram labeled "Closed Circuit (Switch ON)" — same circuit but switch shown as CLOSED (line connected),
current arrows drawn going around the circuit, and the bulb shown as lit (yellow glow around the
symbol). Standard electrical circuit symbols used throughout. Clean white background, blue wires, yellow
highlighted bulb when lit.
Fig. 12.2 — Open circuit vs Closed circuit
🔌 4. Conductors and Insulators
Materials that allow electric current to flow through them are conductors.
Materials that do NOT allow current to flow are insulators.
| Type |
Property |
Examples |
Use in circuits |
| Conductors |
Allow current to flow freely |
All metals (copper, iron, aluminium, silver, gold), graphite, salt water, human body |
Used as wires to carry current |
| Insulators |
Do NOT allow current to flow |
Plastic, rubber, glass, wood, dry air, distilled water, cloth, paper |
Used as coverings on wires for safety |
Electric wires are made of copper (best conductor) and covered with
plastic/rubber (insulator). NEVER touch bare wires or insert metal objects into electric
sockets. Always use dry hands near electricity — water conducts electricity!
🔬 Conductors vs Insulator — Testing Activity:
Experiment: Set up a simple circuit with a cell, bulb, and two clips. Connect different
objects between the clips and observe if the bulb lights up.
- Bulb lights up → material is a conductor
- Bulb stays off → material is an insulator
💡 5. The Electric Bulb
An electric bulb glows when current passes through the thin wire inside it called the filament.
- The filament is made of tungsten (a metal with very high melting point)
- When current passes, the filament becomes very hot and glows bright (due to high resistance)
- The glass bulb is filled with an inert gas (argon or nitrogen) to prevent the
filament from burning out (oxidizing)
- The two terminals (contact pins at the base) connect to the external circuit
📸 Image Prompt
A detailed labeled cross-section diagram of an electric bulb: The glass envelope
(outer glass case), the thin coiled filament inside (tungsten wire), the argon/inert gas filling labeled
inside, the glass support holding the filament, two lead-in wires connecting the filament to the base,
and the metal base contact at the bottom. Each part clearly labeled with an arrow. Show the bulb glowing
with yellow light radiating from the filament. Scientific, educational diagram style, white background.
Fig. 12.3 — Parts of an electric bulb
📝 6. Quick Revision
- Electric current = flow of electrons through a conductor
- Cell = converts chemical energy to electrical energy; has + and − terminals
- Battery = two or more cells connected together
- Electric circuit = complete closed path for current: cell + wire + bulb + switch
- Open circuit (broken) → no current → bulb off. Closed circuit →
current flows → bulb on
- Conductors = allow current (metals, graphite). Insulators = block
current (rubber, plastic, glass)
- Bulb filament = tungsten wire; glows when heated by current
- Bulb filled with argon/inert gas to prevent filament burn-out
- Wet/moist objects are better conductors — never touch electrical items with wet hands
