Electricity – Ohm's Law | Class 10 Science Complete Guide
Electricity – Ohm's Law Kya Hai?
Class 10 Science ke Electricity chapter me Ohm's Law ek fundamental concept hai. Agar aapko voltage, current aur resistance ka relationship samajh aa gaya, to Electricity chapter ke bahut saare numerical questions solve karna easy ho jata hai.
Electricity me jab electric charges kisi conductor ke through flow karte hain, to electric current produce hota hai. Current ke flow ko samajhne ke liye hume teen important quantities ko understand karna hota hai:
- Voltage (V)
- Current (I)
- Resistance (R)
Ohm's Law in teen quantities ke beech relationship establish karta hai.
Constant temperature par:
V ∝ I
Is proportionality ko equation me likhne par:
V = IR
Yahi Ohm's Law ka main formula hai.
Electric Current Kya Hai?
Electric current ko simple language me flow of electric charge kaha ja sakta hai.
Jab electric charges kisi conductor ke through flow karte hain, tab electric current produce hota hai.
Current ka formula hai:
I = Q/t
Yahan:
- I → Electric Current
- Q → Electric Charge
- t → Time
Current ki SI unit Ampere (A) hai.
Ohm's Law Ki Three Important Quantities
1. Voltage (V)
Voltage ko Potential Difference bhi kaha jata hai.
Potential difference ko work done per unit charge ke form me define kiya jata hai.
Voltage ki SI unit:
Volt (V)
Symbol:
V
2. Current (I)
Electric current charge ke flow ki rate ko represent karta hai.
Formula:
I = Q/t
SI unit:
Ampere (A)
Symbol:
I
3. Resistance (R)
Resistance conductor ke through electric current ke flow ka opposition hai.
Resistance jitna zyada hoga, same voltage par current generally utna kam hoga.
Resistance ki SI unit:
Ohm (Ω)
Symbol:
R
Ohm's Law
Ohm's Law ke according, agar temperature aur other physical conditions constant rakhi jayein, to conductor ke across potential difference current ke directly proportional hota hai.
V ∝ I
Proportionality constant ko resistance kehte hain.
Therefore:
V = IR
Is formula ko rearrange karke hum current aur resistance bhi find kar sakte hain:
I = V/R
R = V/I
Ohm's Law Formula Triangle
Ohm's Law ko yaad rakhne ke liye simple formula triangle use kar sakte hain:
V
─────
I R
Jis quantity ko find karna ho, usse cover karne par formula easily yaad aa jata hai.
V = I × R
I = V/R
R = V/I
Rule 1: Voltage Increase Hone Par Kya Hoga?
Agar resistance constant hai, to voltage aur current directly proportional hote hain.
V ↑ → I ↑
Example:
Resistance:
R = 5 Ω
Voltage:
V = 10 V
Current:
I = V/R
I = 10/5 = 2 A
Agar voltage 20 V ho jaye:
I = 20/5 = 4 A
Yahan voltage double hua aur current bhi double ho gaya.
Conclusion: Constant resistance par voltage increase hone se current proportionally increase hota hai.
Rule 2: Resistance Increase Hone Par Kya Hoga?
Agar voltage constant hai, to current resistance ke inversely proportional hota hai.
R ↑ → I ↓
Example:
V = 12 V
R = 4 Ω
Current:
I = 12/4 = 3 A
Agar resistance 6 Ω ho jaye:
I = 12/6 = 2 A
Isliye same voltage par resistance increase hone se current decrease hota hai.
Conclusion: More resistance → Less current.
Rule 3: Unit Conversion
Ohm's Law ke numerical solve karte waqt units ko carefully check karna zaroori hai.
Voltage
1 kV = 1000 V
Current
1 A = 1000 mA
Resistance
1 kΩ = 1000 Ω
⚠️ Formula apply karne se pehle values ko compatible units me convert karein.
How to Find Current?
Agar voltage aur resistance given hain, to current find karne ke liye:
I = V/R
Given:
V = 12 V
R = 4 Ω
Therefore:
I = 12/4
I = 3 A
How to Find Resistance?
Agar voltage aur current given hain, to:
R = V/I
Given:
V = 20 V
I = 4 A
Therefore:
R = 20/4
R = 5 Ω
How to Find Voltage?
Agar current aur resistance given hain, to:
V = IR
Given:
I = 2 A
R = 6 Ω
Therefore:
V = 2 × 6
V = 12 V
Ohm's Law V-I Graph
Ohm's Law ko graphically bhi represent kiya ja sakta hai.
Agar hum V ko Y-axis aur I ko X-axis par plot karein, to an ohmic conductor ke liye graph ek straight line passing through the origin hota hai.
V │ │ / │ / │ / │ / │ / │ / │_/____________ I
Graph ki slope:
Slope = V/I
Ohm's Law se:
R = V/I
Therefore:
Slope = R
Isliye V-I graph ka slope resistance ko represent karta hai.
Important: Steeper V-I graph ka matlab greater resistance hai.
Experimental Verification of Ohm's Law
Ohm's Law ko experimentally verify karne ke liye ek circuit setup banaya jata hai jisme battery, key, ammeter, resistor aur voltmeter ka use hota hai.
Apparatus
- Battery
- Key
- Ammeter
- Resistor
- Voltmeter
- Connecting wires
Circuit Arrangement
┌────── V ──────┐
│ │
+ ── K ── A ── R ───┘ ── -
│ │
└───────────────┘
Yahan:
Ammeter → Series
Voltmeter → Parallel
Ammeter circuit me flow hone wale current ko measure karta hai, isliye ise series me connect kiya jata hai.
Voltmeter resistor ke across potential difference measure karta hai, isliye ise resistor ke parallel connect kiya jata hai.
Observation Table
| V (Volt) | I (Ampere) | V/I |
|---|---|---|
| 2 | 0.4 | 5 Ω |
| 4 | 0.8 | 5 Ω |
| 6 | 1.2 | 5 Ω |
| 8 | 1.6 | 5 Ω |
Table se clearly observe hota hai ki:
V/I = Constant
Since:
R = V/I
Therefore:
R = Constant
Hence, given conditions ke under Ohm's Law verify hota hai.
Why Does Temperature Matter?
Ohm's Law ko apply karte waqt physical conditions constant rehni chahiye. In conditions me temperature particularly important hai.
Metallic conductors ke case me generally:
Temperature ↑ → Resistance ↑
Agar temperature significantly change ho jaye, to conductor ka resistance bhi change ho sakta hai. Is situation me V-I relationship poori range me straight line nahi reh sakta.
Isliye board exam me sirf ye likhna:
V = IR is true for every conductor under all conditions. ❌
Correct statement:
V = IR holds for an ohmic conductor when physical conditions, especially temperature, remain constant. ✅
Ohmic and Non-Ohmic Conductors
Ohmic Conductor
Ohmic conductor wo conductor hota hai jo constant physical conditions ke under Ohm's Law obey karta hai.
Features:
- ✔ Ohm's Law obey karta hai.
- ✔ V-I graph straight line hota hai.
- ✔ Constant temperature par resistance constant rehta hai.
Example:
Metallic resistor
Non-Ohmic Conductor
Non-ohmic conductor Ohm's Law ko poori operating range me obey nahi karta.
Features:
- ❌ V-I graph generally straight line nahi hota.
- ❌ Resistance operating conditions ke saath change ho sakta hai.
Examples:
- Diode
- Filament lamp
Real-Life Analogy
Electricity ko samajhne ke liye water flow ka analogy helpful ho sakta hai.
- Voltage → Pressure pushing water
- Current → Flow of water
- Resistance → Narrowness or opposition in pipe
More pressure se water flow increase ho sakta hai, similarly higher voltage par constant resistance ke case me current increase hota hai.
Similarly, pipe me opposition badhne par flow reduce hota hai, jaise constant voltage par resistance increase hone se current decrease hota hai.
⚠️ Ye sirf ek analogy hai. Electric current literally water flow nahi hai.
Important Formula Box
Electric Current
I = Q/t
Where:
- I → Current
- Q → Charge
- t → Time
Ohm's Law
V = IR
Where:
- V → Potential Difference
- I → Current
- R → Resistance
Resistance
R = V/I
Unit:
1 Ω = 1 V/A
Important Relationships
At Constant Resistance
V ∝ I
Voltage increase hone par current bhi increase hota hai.
At Constant Voltage
I ∝ 1/R
Resistance increase hone par current decrease hota hai.
At Constant Current
V ∝ R
Current constant ho to voltage aur resistance directly proportional hote hain.
Common Mistakes
Class 10 students Ohm's Law ke questions me commonly ye mistakes karte hain:
- ❌ Ammeter ko parallel connect karna.
- ❌ Voltmeter ko series me connect karna.
- ❌ Unit conversion ignore karna.
- ❌ Formula ko I = VR likh dena.
- ❌ Correct formula I = V/R bhool jana.
- ❌ Sochna ki higher resistance ka matlab higher current hota hai.
- ❌ Constant temperature condition ko ignore karna.
- ❌ V-I graph ke axes incorrectly label karna.
- ❌ V-I graph ki slope ko incorrectly current samajhna.
Board Question 1
Question
A resistor of resistance 5 Ω is connected to a 20 V battery. Find the current.
Solution
Given:
V = 20 V
R = 5 Ω
Formula:
I = V/R
Substitute:
I = 20/5
I = 4 A
Answer
Current = 4 A
Board Question 2
Question
A current of 2 A flows through a resistor when a potential difference of 10 V is applied. Find its resistance.
Solution
Given:
V = 10 V
I = 2 A
Formula:
R = V/I
Substitute:
R = 10/2
R = 5 Ω
Answer
Resistance = 5 Ω
Board Question 3
Question
A resistor carries a current of 0.5 A when connected to a 6 V source. Find its resistance.
Solution
Formula:
R = V/I
Substitute:
R = 6/0.5
R = 12 Ω
Answer
Resistance = 12 Ω
Competency-Based Question
A student increases the potential difference across a resistor while keeping its temperature constant. The current also increases proportionally.
Question 1: Which law is being verified?
Answer → Ohm's Law
Question 2: What happens to V/I?
Answer → V/I remains constant
Question 3: What does V/I represent?
Answer → Resistance
Question 4: What will the V-I graph look like?
Answer → A straight line passing through the origin
Quick Trick
Ohm's Law ke liye VIR Triangle yaad rakhein:
V
─────
I R
V = I × R
I = V/R
R = V/I
Instruments ke liye:
Ammeter → Series
Voltmeter → Parallel
2-Minute Revision
Current
→ Flow of electric charge
I = Q/t
Unit = Ampere
↓
Voltage
→ Potential difference
Unit = Volt
↓
Resistance
→ Opposition to current
Unit = Ohm
↓
Ohm's Law
V = IR
↓
V-I Graph
→ Straight line through origin for an ohmic conductor
↓
Slope
V/I = R
Revision Box
- ✔ Ohm's Law → V = IR
- ✔ Current → I = Q/t
- ✔ Resistance → R = V/I
- ✔ Unit of V → Volt
- ✔ Unit of I → Ampere
- ✔ Unit of R → Ohm
- ✔ Ammeter → Series
- ✔ Voltmeter → Parallel
- ✔ V-I Graph → Straight Line through Origin
- ✔ Slope of V-I graph → Resistance
- ✔ Constant temperature → Important condition
- ✔ Ohmic conductor → Obeys Ohm's Law under constant physical conditions
Frequently Asked Questions (FAQs)
Ohm's Law kya hai?
Ohm's Law ke according, constant physical conditions aur temperature par kisi ohmic conductor ke across potential difference current ke directly proportional hota hai. Iska mathematical form V = IR hai.
Ohm's Law ka formula kya hai?
Ohm's Law ka main formula V = IR hai. Isse I = V/R aur R = V/I bhi obtain kiya ja sakta hai.
Current ka formula kya hai?
Electric current ka formula I = Q/t hai, jahan Q charge aur t time ko represent karta hai.
Resistance ki SI unit kya hai?
Resistance ki SI unit Ohm (Ω) hai.
Ammeter ko series me kyu connect karte hain?
Ammeter circuit me flow hone wale current ko measure karta hai, isliye ise circuit ke series me connect kiya jata hai.
Voltmeter ko parallel me kyu connect karte hain?
Voltmeter kisi component ke across potential difference measure karta hai, isliye ise component ke parallel connect kiya jata hai.
V-I graph ka slope kya represent karta hai?
Agar V ko Y-axis aur I ko X-axis par plot kiya jaye, to slope V/I hoti hai. Ohm's Law ke according V/I = R, isliye slope resistance represent karta hai.
Ohm's Law ke liye temperature constant kyu hona chahiye?
Temperature change hone par metallic conductor ka resistance change ho sakta hai. Isliye Ohm's Law ki proportional relationship ko verify karne ke liye physical conditions, especially temperature, constant rakhna important hai.
Ohmic aur Non-Ohmic conductor me kya difference hai?
Ohmic conductor constant physical conditions par Ohm's Law obey karta hai aur uska V-I graph straight line hota hai. Non-ohmic conductor poori range me Ohm's Law obey nahi karta aur uska V-I graph generally straight line nahi hota.
Download PDF Notes
Class 10 Science revision ke liye Electricity – Ohm's Law ke PDF notes ko yahan directly read kar sakte hain:
Final Thoughts
Ohm's Law Class 10 Science ke Electricity chapter ka ek fundamental concept hai. Is law ke through hum voltage, current aur resistance ke beech relationship ko samajh sakte hain. Sabse important formula hai V = IR, jise rearrange karke I = V/R aur R = V/I bhi use kiya ja sakta hai.
Board Exam ke liye voltage, current aur resistance ki definitions ke saath unki SI units ko bhi clearly yaad rakhein. Current ki unit Ampere, voltage ki unit Volt aur resistance ki unit Ohm hai.
Ohm's Law ke numericals solve karte waqt sabse pehle given values identify karein, units check karein, correct formula select karein aur final answer ke saath proper unit zaroor likhein.
Graph-based questions me yaad rakhein ki V ko Y-axis aur I ko X-axis par plot karne par ohmic conductor ke liye straight line through origin milti hai. Is graph ki slope V/I = R hoti hai. Isliye steeper V-I graph greater resistance indicate karta hai.
Circuit questions ke liye ek golden rule yaad rakhein: Ammeter → Series aur Voltmeter → Parallel. Temperature aur other physical conditions constant rakhna bhi Ohm's Law ki validity ke liye important hai.
Ohm's Law ko revise karte waqt bas ye flow yaad rakhiye:
Voltage → Current → Resistance → V = IR → V-I Graph → Slope = Resistance
Agar aap formulas, graphs, circuit arrangement aur numerical questions ki regular practice karte hain, to Electricity chapter ke Ohm's Law based questions ko confidently solve kar sakte hain.
Class 10 Board Exam ke liye Ohm's Law ka formula hi nahi, balki uski condition, graph aur practical circuit arrangement bhi zaroor revise karein.