State and apply Ohm's Law (V = IR) — Hinglish notes

1.1.6 · Hardware › Electricity & Charge Basics

Ohm's Law HAI KYA?

Key word hai proportional: voltage double karo, current double ho jaata hai — jab tak $R$ constant rahe (jiske liye constant temperature chahiye).

YEH SACH KYU HAI? (First principles se derivation)

Hum sirf $V = I R$ state nahi karte — hum ise build karte hain.

Formula V = IR ko definitions se build karna

Step 1 — Resistance define karo. Resistance measure karta hai ki kisi cheez mein se current push karna kitna mushkil hai. "Opposition to flow" ki natural definition hai: $R \equiv \frac{V}{I}$ Yeh step kyun? Opposition = (kitna push chahiya tha) ÷ (kitna flow mila). Bada push deke tiny flow milna matlab bada resistance.

Step 2 — Experimental fact observe karo (Ohm ki discovery). Ohm ne metal wires ke liye $V$ aur $I$ measure kiye aur paaya ki ratio $V / I$ constant rehta hai jab $V$ change karo. Woh constant hi $R$ hai. Yeh kyun matter karta hai: Agar $R$ $V$ ke saath change hota, toh hum ise simple law nahi keh sakte. Ohmic materials ka magic yeh hai ki $R$ ek fixed number hai.

Step 3 — Rearrange karo. Kyunki $R = V / I$ constant hai, dono sides ko $I$ se multiply karo: $V = I R$ Yeh step kyun? Ab yeh ek predictive tool hai: koi bhi do quantities do, teesri nikal lenge.

KAISE apply karein — triangle trick

Teeno forms ek hi equation par algebra hain:

$V = I R I = \frac{V}{R} R = \frac{V}{I}$

Mnemonic VIR Triangle

Ek triangle banao:

      V
     -----
    I  |  R

Jo quantity chahiye usse cover karo:

V cover karo → $I \times R$ dikhega
I cover karo → $V / R$ dikhega
R cover karo → $V / I$ dikhega "V upar baithta hai (boss), I aur R neeche share karte hain."

Figure — State and apply Ohm's Law (V = IR)

Worked Examples

Common Mistakes (Steel-manned)

V–I Graph padhna

Active Recall

Recall Q: Ohm's Law words aur symbols mein state karo.

Ohmic conductor se guzarne wala current constant temperature par us par lage voltage ke directly proportional hota hai: $V = I R$ .

Recall Q: I aur R ke liye rearrange karo.

$I = V / R$ aur $R = V / I$ .

Recall Q: Resistance kya hai agar 8 V par 4 A flow kare?

$R = V / I = 8/4 = 2 Ω$ .

Recall Q: Temperature constant kyun honi chahiye?

Kyunki heating R ko change karti hai (zyada lattice vibration → zyada electron collisions → higher R), jo proportionality tod deta hai.

Recall Q: Ek ohmic resistor ke V–I graph par gradient kya represent karta hai?

Resistance $R$ .

Recall Feynman: ek 12-saal ke bacche ko explain karo.

Socho kids ko slide par push kar rahe ho. Voltage hai kitni steep slide banate ho (push). Current hai kitne kids har second neeche pohunchte hain. Resistance hai slide kitni sticky/rough hai. Zyada steep banao (zyada voltage) toh zyada kids slide karte hain (zyada current). Zyada sticky banao (zyada resistance) toh kam pohunchte hain. Formula $V = I R$ bas kehta hai: steepness = kids-per-second × stickiness.

80/20 — Woh 20% jo kabhi nahi bhoolna

$V = I R$ aur uske do rearrangements.
Units: V, A, Ω — pehle mA/kΩ convert karo.
Ohmic ⇒ R constant ⇒ straight-line V–I graph, gradient = R.
V across hota hai (parallel), I through hota hai (series).

Flashcards

Ohm's Law equation

V = I R

Ohm's Law ko current ke liye rearrange karo

I = V / R

Ohm's Law ko resistance ke liye rearrange karo

R = V / I

Resistance ki unit

Ohm (Ω)

Current ki unit

Ampere (A)

Potential difference ki unit

Volt (V)

Ohm's Law mein "directly proportional" ka matlab kya hai?

V double karne se I double hota hai jab R constant ho

Ohm's Law hold karne ki condition

Constant temperature (ohmic conductor)

250 mA ko amperes mein convert karo

0.25 A

4.7 kΩ ko ohms mein convert karo

4700 Ω

V (y) vs I (x) graph ka gradient

Resistance R

Ohmic resistor ke V–I graph ki shape

Origin se guzarti straight line

Shortcut: mA × kΩ = ?

Volts (factors cancel ho jaate hain)

Voltage ek component ke ___ measure hota hai; current ___

across; through

I nikalo: 12 V across 6 Ω

2 A

R nikalo: 9 V, 0.5 A

18 Ω

Wire heat hone par R kyun barhta hai?

Atoms zyada vibrate karte hain → zyada electron collisions → higher resistance

Kya filament lamp ohmic hai?

Nahi — heat hone par R barhta hai, isliye V–I curve bend hoti hai

Connections

Electric Current — formula mein $I$ (charge flow per second)
Potential Difference (Voltage) — $V$ , energy per unit charge
Resistance — $R$ , plus resistivity aur geometry
Series and Parallel Circuits — resistances combine karna, jahan V/I placement matter karta hai
Power in Circuits (P = VI) — Ohm's Law ke saath combine hokar $P = I^{2} R = V^{2} / R$ deta hai
Non-ohmic Components — diodes, filament lamps jahan R vary karta hai