🧭 Chapter Overview
Electricity powers our homes, industries, schools, and even our hearts (through electrical impulses!).
But electricity is more than just light bulbs and fans — it can produce heat, light, and magnetism.
In this chapter, we’ll explore:
- How electrical energy transforms into heat (heating effect)
- How electricity can create a magnetic field (magnetic effect)
- Practical applications like fuses, electromagnets, and electric motors
By the end, you’ll not only understand the science behind circuits but also how electricity shapes our daily life — from the switch in your home to trains running on electromagnets!
Table of Contents
🎯 Learning Objectives (NEP 2025 Competency Table)
| Competency | Learning Outcome | NEP Skill |
|---|---|---|
| Conceptual Understanding | Explain heating and magnetic effects of current | Conceptual Clarity |
| Inquiry & Investigation | Observe current flow & experiment with electromagnets | Scientific Temper |
| Application | Relate electrical concepts to daily life | Practical Learning |
| Analytical | Understand safety devices and their role | Critical Thinking |
| Ethical Awareness | Use electricity responsibly & conserve energy | Sustainability |
🔌 4.1 What Is Electric Current?
Electric current is the flow of electrons through a conductor (like a copper wire).
It always flows from the positive terminal to the negative terminal of a cell in a circuit diagram.
| Symbol | Component | Function |
|---|---|---|
| 🔋 | Cell | Source of electric energy |
| ⚡ | Battery | Combination of cells |
| 💡 | Bulb | Converts electric energy to light & heat |
| 📏 | Wire | Conducts current |
| 🔘 | Switch | Opens or closes the circuit |
🧪 Activity – Checking for a Complete Circuit
Aim: To test if a circuit is complete.
Materials: Cell, wire, and bulb.
Process: Connect wires from the cell to the bulb.
Observation: The bulb glows only when the circuit is closed, showing current flow.
⚡ A closed circuit = flow of electricity. An open circuit = no current.
🔥 4.2 Heating Effect of Electric Current
When an electric current passes through a wire, it gets hot.
This is called the heating effect of electric current.
The heating happens because electrons collide with atoms in the wire, transferring energy as heat.
⚙️ Joule’s Law of Heating
H=I2RtH = I^2 R tH=I2Rt
where,
H = Heat produced
I = Current (in Amperes)
R = Resistance (in Ohms)
t = Time (in seconds)
So, more current = more heat.
💡 Everyday Examples of Heating Effect
| Device | Purpose | Explanation |
|---|---|---|
| Electric Iron | Iron clothes | Coil gets heated |
| Geyser | Heat water | Converts electricity to heat |
| Toaster | Bake bread | Heating element glows red |
| Bulb (filament type) | Light | Tungsten filament heats & emits light |
🧩 Activity: Heating Coil Experiment
Aim: Observe heating effect.
Procedure:
- Connect a thin nichrome wire to a battery.
- After a few seconds, touch (carefully near ends).
- You’ll feel it’s warm → current produces heat.
Conclusion:
Thinner and longer wires heat up faster due to higher resistance.
⚠️ Electric Fuse – A Safety Hero
When current exceeds a safe limit, wires can overheat and cause fires.
A fuse protects electrical circuits by melting and breaking the circuit when excess current flows.
| Component | Material | Function |
|---|---|---|
| Fuse wire | Tin + Lead | Melts easily when overheated |
| Circuit breaker | Automatic switch | Replaces traditional fuse |
🧠 Fuse acts like a bodyguard — it sacrifices itself to save the circuit.
🧲 4.3 Magnetic Effect of Electric Current
Discovered by Hans Christian Ørsted (1820), who noticed that a current-carrying wire deflects a nearby compass needle.
This proved that electric current produces a magnetic field.
🧪 Activity: Current and Compass
Materials: Battery, wire, compass.
Steps:
- Place a compass under a wire.
- Pass current through the wire.
- The needle moves → magnetic field produced!
Inference:
Electric current can act like a magnet — this is the magnetic effect of electric current.
⚙️ Right-Hand Thumb Rule
If you hold the wire with your right hand, thumb pointing in current’s direction,
then the curl of fingers shows the direction of the magnetic field.
🌀 Field lines form concentric circles around the wire.
🧭 Magnetic Field Around a Coil
When current passes through a circular loop, magnetic field lines become stronger at the center.
Winding several loops forms a solenoid, which behaves like a bar magnet.
🧲 4.4 Electromagnet
An electromagnet is a temporary magnet made by passing current through a coil around a soft iron core.
🧪 Activity: Making an Electromagnet
Aim: To make a simple electromagnet.
Materials: Iron nail, wire, battery.
Process:
- Wind the wire around the nail.
- Connect both ends to the battery.
- The nail attracts pins or paperclips.
Observation:
Magnetism appears when current flows and disappears when stopped.
🔁 Reversible magnetism = electromagnetism.
⚡ Applications of Electromagnets
| Device | Use |
|---|---|
| Electric Bell | Produces sound by magnetizing and demagnetizing an iron hammer |
| Electric Motor | Converts electrical energy to mechanical energy |
| Cranes | Lifting heavy iron scrap |
| MRI Machines | Imaging body organs using magnetic fields |
🔔 4.5 How an Electric Bell Works
An electric bell is an application of electromagnetism.
Components:
Iron hammer, electromagnet, armature, contact screw, gong, switch.
Working:
- When switch ON → current flows through coil → electromagnet forms.
- Magnet attracts iron armature → hammer hits gong (sound).
- Circuit breaks → magnetism lost → armature returns.
- Cycle repeats rapidly → bell rings continuously.
🔁 4.6 The Electric Motor – Heart of Machines
An electric motor converts electrical energy → mechanical energy.
It works on the magnetic effect of current.
🧩 Basic Principle
When a current-carrying coil is placed in a magnetic field, it experiences a force that causes it to rotate.
Applications:
- Fans, mixers, washing machines, and electric vehicles.
💡 Motors turn electricity into motion – one of the most powerful human inventions.
⚡ 4.7 Energy Conservation & Electrical Safety
⚙️ Safety Tips
✅ Never touch switches or wires with wet hands
✅ Use insulated tools
✅ Switch off unused devices
✅ Replace damaged plugs & wires
✅ Use proper fuse rating
🌱 Save Electricity
💡 Use LED bulbs instead of filament bulbs.
🌞 Use natural light during day.
🧺 Switch off appliances when not in use.
♻️ Promote renewable energy (solar, wind, hydro).
“Energy saved = Energy produced.”
🧠 HOTS (Higher Order Thinking Skills)
- Why does a bulb’s filament glow but not the connecting wires?
- Why does a thick wire produce less heat than a thin one?
- Why is iron preferred for making electromagnets instead of steel?
- How do electric motors in washing machines work?
- Why is copper used for electrical wiring?
⚙️ NEP COMPETENCY FRAMEWORK
| Domain | Skill | Example Activity |
|---|---|---|
| Conceptual | Understand electricity & magnetism link | Compass and circuit activity |
| Analytical | Apply Joule’s Law | Calculate heat in a circuit |
| Practical | Construct electromagnet | Lab demonstration |
| Creative | Build working model | Mini electric bell project |
| Ethical | Save energy responsibly | Energy audit at home |
💡 Memory Booster Box
🔹 Electric current = flow of electrons
🔹 Heating effect = current produces heat (H = I²Rt)
🔹 Magnetic effect = current produces magnetic field
🔹 Electromagnet = temporary magnet using current
🔹 Electric bell = electromagnet + hammer
🔹 Motor = converts electricity to motion
⚠️ Exam Alert Box
📍 Define: Electromagnet, Heating Effect, Fuse
📍 Differentiate: Magnetic vs Heating Effects
📍 Explain: Working of electric bell
📍 Formula: Joule’s Law of Heating
📍 Value Question: Why should we save electricity?
📘 Quick Recap
✅ Electric current causes heat and magnetism
✅ Heat depends on current, resistance, and time
✅ Magnetic field forms around current-carrying wires
✅ Electromagnets are used in bells & cranes
✅ Electric motors convert electricity into movement
✅ Conserve electricity for a sustainable future 🌱
🔗 INTERNAL & EXTERNAL LINKS
Internal Links (A2ZLY):
- Chapter 3 – Health: The Ultimate Treasure Notes 2025
- Chapter 5 – Sound: Vibrations and Waves Notes 2025
- Smart Notes Creator Science Hub | A2ZLY
External Links: