Define voltage (potential difference) and its units

1.1.3 · Hardware › Electricity & Charge Basics

Voltage KYUN exist karta hai?

Charges electric fields create karte hain. Ek positive charge ko us field ke against move karne ke liye (maano, ek low-energy jagah se high-energy jagah tak), tumhe us par work karna padta hai — bilkul jaise ek patthar ko gravity ke against uthane se gravitational potential energy store hoti hai.

Woh stored energy, charge ke har coulomb ke hisaab se measure ki gayi, electric potential kehlati hai. Do points ke beech is stored-energy-per-charge ka fark hi hum voltage kehte hain.

Voltage precisely KIYA hai?

Ek zaroori baat: Voltage hamesha do points ke beech hota hai. Ek akele point ka apna koi voltage nahi hota jab tak hum koi reference ("ground", aam taur par 0 V) na chunein. "Node X par voltage 5 V hai" kehna secretly matlab hai "ground ke relative 5 V."

Units ko first principles se KAISE derive karein?

Hum volt ko jo pehle se jaante hain usse build karte hain, koi memorization nahi:

Work / Energy force × distance hai: $W = F \cdot d$ , unit = joule (J).
Charge coulombs (C) mein measure hota hai.
Voltage energy per charge ke roop mein define hoti hai: $V = \frac{W}{q} = \frac{joules}{coulombs} = \frac{J}{C}$
Hum is ratio ko volt naam dete hain. Bas itna hi — volt fundamental nahi hai; yeh J/C ka shorthand hai.

Figure — Define voltage (potential difference) and its units

Worked Examples

Forecast-then-Verify

Recall Compute karne se pehle Forecast karo

Q: Agar tum do fixed points ke beech move kiye jaane wale charge ko double kar do lekin same field rakho, toh kya un points ke beech voltage badlega? Apna jawab forecast karo, phir reveal karo: A: Nahi. Voltage do points ki property hai (energy per charge). $q$ double karne se work $W$ double hota hai, lekin $V = W / q$ same rehta hai. "Pahaad ki unchaai" nahi badlti.

Common Mistakes (Steel-manned)

#flashcards/hardware

Potential difference (voltage) ki definition kya hai?

Do points ke beech charge move karne mein laga work per unit charge,

V = W / q

Voltage ki SI unit kya hai aur uski base definition?

Volt (V);

1 V = 1 J/C

(ek joule per coulomb).

Voltage hamesha "do points ke beech" kyun measure hota hai?

Kyunki yeh energy-per-charge mein ek difference hai; ek akele point ko defined value ke liye reference (ground) chahiye.

Agar do fixed points ke beech move kiya gaya charge triple kar dein, toh voltage ka kya hoga?

Kuch nahi —

V = W / q

; work bhi triple hoga, toh ratio same rehega.

Volt ke units first principles se derive karo.

Energy joules mein hai, charge coulombs mein; voltage = energy/charge = J/C = volt.

V = W / q

ko energy nikalne ke liye rearrange karo.

W = q V

P = V I

voltage se kaise derive hota hai?

P = W / t = q V / t = V (q / t) = V I

I = q / t

use karke.

Ek 9 V battery 0.5 C move karti hai. Kitni energy?

W = q V = 0.5 \times 9 = 4.5

Recall Feynman: ek 12-saal ke bachche ko explain karo

Ek water slide socho. Slide ka top jitna uuncha hoga, paani utni tezi se neeche aayega. Voltage us slide ki unchaai jaisi hai — yeh woh push hai jo tiny electric charges ko move karna chahti hai. Ek 9-volt battery, 1.5-volt battery se uunchi slide hai, toh yeh zyada push karti hai. Aur yahan trick hai: hum push ko paani ki ek bund ke hisaab se (per unit of charge) measure karte hain, toh koyi fark nahi padta kitna paani bhejo — slide ki unchaai same rehti hai. Woh "push per charge" voltage hai, aur hum ise volts mein count karte hain, jahan 1 volt matlab hai 1 unit charge move karne mein 1 unit energy lagti hai.

Connections

Electric charge and the coulomb — voltage per coulomb define hota hai.
Electric current and the ampere — current $I = q / t$ , $V$ ke saath combine hokar power deta hai.
Electric field and potential energy — voltage, potential energy per charge hai.
Ohm's Law V=IR — ek resistor ke across voltage.
Power in electric circuits P=VI — seedha voltage se derive hota hai.
Batteries and EMF — ek source jo fixed potential difference maintain karta hai.