⚡ 1. Electric Circuit — The Basics
An electric circuit is a closed path through which electric current flows.
Current cannot flow if the circuit is open (broken).
Essential parts of a circuit:
- ⚡ Cell / Battery — provides electrical energy (source of EMF). A battery =
two or more cells connected
- 💡 Bulb / Resistor — uses electrical energy (converts to light/heat)
- 🔌 Switch (Key) — opens or closes the circuit (controls current flow)
- 🔗 Connecting Wires — made of copper/aluminium (conductors) to allow current to
flow through
Circuit Diagram Symbols
📸 AI Image Prompt
An educational chart showing standard electrical circuit symbols, arranged in a
neat 3-column grid on a white background. Each entry shows: (1) the symbol (drawn in black on white),
(2) its name in bold, and (3) a brief description. Symbols to include: Cell (two vertical lines, longer
thin one = positive, shorter thick one = negative, with + and − labels), Battery (multiple cell symbols
in series), Bulb/Lamp (circle with crossed filament inside), Switch Open (a gap in the line, showing
circuit is "OFF"), Switch Closed (line connected, circuit is "ON"), Resistor (rectangle or jagged line),
Ammeter (circle with A inside), Voltmeter (circle with V inside), Wire (straight horizontal line), Wire
Junction (dot where wires cross), Earth/Ground (three horizontal lines getting shorter). Also show one
complete example circuit: Battery → Switch → Bulb → back to Battery, drawn with proper symbols in a
rectangular loop. Labels: "When switch is OPEN — no current flows, bulb is OFF. When switch is CLOSED —
current flows, bulb glows." Clean, academic circuit diagram style, black on white.
Fig. 10.1 — Standard circuit symbols and a simple complete circuit diagram
🔥 2. Effects of Electric Current
⚡ Effects of Electric Current
⬇
1. HEATING EFFECT 🌡️
Current flowing
through a wire generates heat (wire's resistance converts electrical energy to heat
energy).
Applications: Electric iron, heater, toaster, electric kettle, fuse
wire, tungsten filament bulb
2. MAGNETIC EFFECT 🧲
A current-carrying wire
creates a magnetic field around it. Winding the wire into a coil amplifies this magnetism →
Electromagnet
Applications: Electric bell, electric motor,
MRI machines, cranes in scrapyards
3. CHEMICAL EFFECT 🧪
Passing current through
certain solutions causes a chemical reaction. Called
Electrolysis.
Applications: Electroplating, purification of
metals, electroforming
🧲 3. Electromagnet — How It Works
An electromagnet is a temporary magnet made by passing electric current through
a coil of wire wound around an iron core.
How to make an electromagnet:
- Take an iron nail (the core)
- Wind insulated copper wire (many turns/coils) around it — this is called a solenoid
- Connect the ends of the wire to a battery through a switch
- When switch is closed → current flows → nail becomes a temporary magnet
- When switch is opened → current stops → nail loses magnetism immediately
Strength of electromagnet increases when you:
- Increase the number of turns/coils of wire
- Increase the current (use more cells/batteries)
- Use an iron core (instead of air core)
🔔 4. Electric Bell — How It Works
Circuit closed → Current flows through coil
⬇
Coil becomes ELECTROMAGNET → attracts iron strip
(armature) toward it
⬇
Hammer hits the bell → DING! 🔔
⬇
As armature moves toward coil, it breaks contact with
contact screw → circuit OPENS → current stops → coil loses magnetism
⬇
Armature springs BACK → circuit closes again →
cycle repeats! → Continuous ringing
🛡️ 5. Fuse — Safety Device
A fuse is a short piece of thin wire (made of a metal with a low
melting point, e.g. copper-tin alloy) connected in series in a circuit. If too much current
flows (short circuit, overloading) → fuse wire gets very hot → melts and breaks → circuit
opens → appliances are protected from damage.
Modern alternative: MCB (Miniature Circuit Breaker) — automatically switches off when
current exceeds safe limit; can be reset (reusable), unlike fuse wire (must be replaced each time it blows).
📝 6. Quick Revision
- A circuit needs: Cell, Switch, Bulb/Resistor, Connecting Wires in a closed loop
- Heating effect: Current generates heat in resistance wire. E.g. electric iron, bulb
filament, fuse
- Magnetic effect: Current through a coil creates a magnetic field → Electromagnet
- Chemical effect: Electrolysis — current through a solution causes chemical change →
Electroplating
- Electromagnet: iron nail + wire coil + current → temporary magnet; stronger with more coils, more
current
- Electric bell: electromagnet repeatedly attracts and releases armature → continuous ringing
- Fuse: thin wire with low melting point; melts if excess current flows → protects
circuit
- MCB = modern replaceable fuse; can be reset without replacing wire
