⚡ CLASS 10 PHYSICS — ELECTRICITY FULL MASTER NOTES
CBSE BOARD 2026 | NCERT BASED | FORMULAS + NUMERICALS + PYQs + DIAGRAMS
📖 INTRODUCTION
Electricity is one of the most important forms of energy used in daily life.
Uses of Electricity:
- Fans
- Bulbs
- Mobile charging
- Computers
- Industries
Important for CBSE Boards:
- Numericals are frequently asked
- Circuit diagrams are important
- Ohm’s Law and Power formulas are very important
🌟 ELECTRIC CURRENT ⭐ VERY IMPORTANT
Electric current is the rate of flow of electric charges through a conductor.
🌟 Formula of Current
Where:
- I = Current (Ampere)
- Q = Charge (Coulomb)
- t = Time (Second)
🌟 SI UNIT OF CURRENT
- Ampere (A)
🌟 1 Ampere
When 1 coulomb charge flows in 1 second.
🌟 ELECTRIC CURRENT DIAGRAM
(+ Battery -) ─────▶ Current Flow
🌟 ELECTRIC POTENTIAL DIFFERENCE ⭐
Work done to move unit charge from one point to another.
🌟 Formula
Where:
- V = Potential Difference (Volt)
- W = Work Done (Joule)
- Q = Charge (Coulomb)
🌟 SI UNIT
- Volt (V)
🌟 ELECTRIC CIRCUIT ⭐
A closed conducting path through which current flows.
🌟 ELECTRIC CIRCUIT DIAGRAM
+| |− ─── Switch ─── Bulb
🌟 ELECTRIC COMPONENTS
| Component | Symbol |
|---|---|
| Cell | — |
| Battery | — |
| Bulb | ⊗ |
| Switch | —o/ o— |
| Ammeter | (A) |
| Voltmeter | (V) |
🌟 OHM’S LAW ⭐ VERY IMPORTANT
According to Ohm’s law:
Current flowing through a conductor is directly proportional to the potential difference across it provided temperature remains constant.
🌟 Formula
Other Forms
Where:
- V = Voltage
- I = Current
- R = Resistance
🌟 OHM’S LAW TRIANGLE TRICK 🧠
V
-----
I R
🌟 RESISTANCE ⭐
Property of conductor that opposes flow of current.
🌟 SI UNIT
- Ohm (Ω)
🌟 FACTORS AFFECTING RESISTANCE
Resistance depends on:
- Length of conductor
- Area of cross-section
- Material
- Temperature
🌟 RESISTANCE FORMULA
Where:
- ρ = Resistivity
- l = Length
- A = Area of cross-section
🌟 RESISTIVITY ⭐ IMPORTANT
Property of material resisting electric current.
🌟 SERIES COMBINATION OF RESISTORS ⭐
Resistors connected one after another.
🌟 SERIES CIRCUIT DIAGRAM
Battery ─ R₁ ─ R₂ ─ R₃
🌟 CHARACTERISTICS OF SERIES COMBINATION
- Same current flows
- Voltage divides
- Equivalent resistance increases
🌟 Formula
Current in Series
Voltage Division
🌟 PARALLEL COMBINATION ⭐ VERY IMPORTANT
Resistors connected between same two points.
🌟 PARALLEL CIRCUIT DIAGRAM
R₁
Battery ─┬─
├─ R₂
└─ R₃
🌟 CHARACTERISTICS OF PARALLEL COMBINATION
- Same voltage across each resistor
- Current divides
- Equivalent resistance decreases
🌟 Formula
Current Division
Voltage in Parallel
🌟 HEATING EFFECT OF CURRENT ⭐
When electric current passes through conductor, heat is produced.
🌟 JOULE’S LAW OF HEATING ⭐ VERY IMPORTANT
Heat produced is directly proportional to:
- Square of current
- Resistance
- Time
🌟 Formula
Other Forms
🌟 APPLICATIONS OF HEATING EFFECT
- Electric iron
- Heater
- Electric kettle
- Fuse
🌟 ELECTRIC FUSE ⭐ VERY IMPORTANT
Safety device protecting appliances.
🌟 WORKING OF FUSE
Fuse wire melts when current becomes excessive.
🌟 ELECTRIC POWER ⭐ VERY IMPORTANT
Rate of consumption of electrical energy.
🌟 Power Formula
🌟 Using Ohm’s Law
🌟 SI UNIT OF POWER
- Watt (W)
🌟 COMMERCIAL UNIT OF ELECTRICAL ENERGY ⭐
Kilowatt-hour (kWh)
🌟 1 Unit of Electricity
🌟 ELECTRICAL ENERGY FORMULA
Other Form
🌟 ELECTRICITY METER DIAGRAM
Main Supply → Meter → House Wiring
🌟 IMPORTANT DIFFERENCES ⭐
Ammeter vs Voltmeter
| Ammeter | Voltmeter |
|---|---|
| Measures current | Measures voltage |
| Connected in series | Connected in parallel |
| Low resistance | High resistance |
Series vs Parallel Combination
| Series | Parallel |
|---|---|
| Same current | Same voltage |
| Resistance increases | Resistance decreases |
| One bulb fused affects all | Others continue working |
Conductor vs Insulator
| Conductor | Insulator |
|---|---|
| Allows current flow | Opposes current |
| Example: Copper | Example: Rubber |
🌟 NUMERICAL FORMULAS ⭐ VERY IMPORTANT
Current Formula
Ohm’s Law
Power Formula
Heat Formula
Energy Formula
🎯 MOST IMPORTANT BOARD QUESTIONS WITH ANSWERS
Q1. State Ohm’s law.
Answer:
According to Ohm’s law, current flowing through conductor is directly proportional to potential difference across it provided temperature remains constant.
Q2. Define resistance.
Answer:
Resistance is the property of conductor that opposes flow of electric current.
Q3. Why are household appliances connected in parallel?
Answer:
Household appliances are connected in parallel so that:
- Each appliance gets same voltage
- Appliances work independently
Q4. What is electric power?
Answer:
Rate of consumption of electrical energy is called electric power.
Q5. Define 1 kWh.
Answer:
Energy consumed by a 1000 watt appliance in 1 hour is called 1 kilowatt-hour.
🔥 IMPORTANT NCERT POINTS
- Current flows from higher to lower potential.
- Ammeter connected in series.
- Voltmeter connected in parallel.
- Fuse prevents damage.
- Parallel combination used in homes.
🧠 SUPER TRICKS
Ohm’s Law Triangle
V
-----
I R
Power Formula Trick — “VIP”
- V → Voltage
- I → Current
- P → Power
Heating Effect Trick — “HIRT”
- H = Heat
- I² = Current square
- R = Resistance
- T = Time
✍️ MOST IMPORTANT DIAGRAMS FOR BOARDS
- Electric circuit
- Series combination
- Parallel combination
- Fuse diagram
- Ohm’s law graph
🎯 EXPECTED QUESTIONS FOR CBSE BOARD 2026
- State Ohm’s law.
- Explain series and parallel combinations.
- Define electric power and electrical energy.
- Explain heating effect of current.
- Why are household circuits connected in parallel?
- Differentiate ammeter and voltmeter.
- Explain electric fuse.
- Derive formula for equivalent resistance in series combination.
