SI units — seven base units and all derived units

1.1.2 · Physics › Measurement, Vectors & Kinematics

SI ki zaroorat KYU hai?

SAAT base quantities kya hain?

Definition The seven SI base units

Base quantity	Symbol	Unit name	Unit symbol
Length	$L$	metre	$m$
Mass	$M$	kilogram	$kg$
Time	$T$	second	$s$
Electric current	$I$	ampere	$A$
Thermodynamic temperature	$Θ$	kelvin	$K$
Amount of substance	$N$	mole	$mol$
Luminous intensity	$J$	candela	$cd$

YEH SAAT HI KYU, aur koi nahi? Inhe isliye choose kiya gaya hai kyunki yeh dimensionally independent hain: inme se koi bhi doosron ke combination se nahi banta. "Time" ko length aur mass se nahi bana sakte, wagera. Yeh physical dimensions ke "vector space" ka ek basis form karte hain.

Figure — SI units — seven base units and all derived units

Base units ab KAISE define hote hain (2019 redefinition)

Derived units — recipe machine

Newton scratch se derive karo

$F = ma \Rightarrow [F] = [m] [a] = kg \cdot \frac{m}{s ^{2}} = kg\cdotm\cdots^{- 2} \equiv 1 N$ Yeh step kyun? Acceleration hai "metres per second, per second" $= m/s^{2}$ , aur force hai mass times that. Kuch yaad nahi karna — equation hi recipe hai.

Joule (energy) derive karo

$W = F \cdot d \Rightarrow [W] = N\cdotm = kg\cdotm^{2} \cdots^{- 2} \equiv 1 J$ Kyun? Work = force along a distance, toh force unit ko metre se multiply karo.

Watt (power) derive karo

$P = \frac{W}{t} \Rightarrow [P] = \frac{J}{s} = kg\cdotm^{2} \cdots^{- 3} \equiv 1 W$

Pascal (pressure) derive karo

$p = \frac{F}{A} \Rightarrow [p] = \frac{N}{m ^{2}} = kg\cdotm^{- 1} \cdots^{- 2} \equiv 1 Pa$

Coulomb aur volt derive karo

$Q = I t \Rightarrow [Q] = A\cdots \equiv 1 C$ $V = \frac{W}{Q} \Rightarrow [V] = \frac{J}{C} = kg\cdotm^{2} \cdots^{- 3} \cdotA^{- 1} \equiv 1 V$ Kyun? Charge = current × time (current hi hai charge-per-time). Voltage = energy per unit charge.

Formula Common derived units ka reference table

Quantity	Unit	In named units	In base units
Frequency	hertz (Hz)	—	$s^{- 1}$
Force	newton (N)	—	$kg\cdotm\cdots^{- 2}$
Pressure	pascal (Pa)	$N/m^{2}$	$kg\cdotm^{- 1} s^{- 2}$
Energy/Work	joule (J)	$N\cdotm$	$kg\cdotm^{2} s^{- 2}$
Power	watt (W)	$J/s$	$kg\cdotm^{2} s^{- 3}$
Charge	coulomb (C)	$A\cdots$	$A\cdots$
Potential	volt (V)	$J/C$	$kg\cdotm^{2} s^{- 3} A^{- 1}$
Resistance	ohm ( $Ω$ )	$V/A$	$kg\cdotm^{2} s^{- 3} A^{- 2}$
Capacitance	farad (F)	$C/V$	$A^{2} s^{4} kg^{- 1} m^{- 2}$
Magnetic flux	weber (Wb)	$V\cdots$	$kg\cdotm^{2} s^{- 2} A^{- 1}$
Mag. flux density	tesla (T)	$Wb/m^{2}$	$kg\cdots^{- 2} A^{- 1}$

Worked examples

Common mistakes (steel-manned)

Recall Feynman: ek 12-saal ke bacche ko samjhao

Socho ek LEGO set hai jisme sirf 7 khaas starter bricks hain: ek ruler-brick (metre), ek weight-brick (kilogram), ek clock-brick (second), ek electricity-brick (ampere), ek hotness-brick (kelvin), ek counting-brick (mole), aur ek brightness-brick (candela). Har doosra measuring tool — speed, push, energy, kuch bhi — in 7 bricks ko kisi pattern mein snap karke banta hai. Toh tumhe kabhi naya brick nahi banana; bas science equation dekho aur sahi starter bricks snap karo.

Active-recall flashcards

#flashcards/physics

SI base units kitne hote hain?

Saat.

Saat SI base units ke naam batao.

metre, kilogram, second, ampere, kelvin, mole, candela.

Electric current ka SI base unit?

ampere (A).

Amount of substance ka SI base unit?

mole (mol).

Luminous intensity ka SI base unit?

candela (cd).

Newton ka base-unit form?

kg\cdotm\cdots^{- 2}

(

F = ma

se).

Joule ka base-unit form?

kg\cdotm^{2} \cdots^{- 2}

(

W = F d

se).

Watt ka base-unit form?

kg\cdotm^{2} \cdots^{- 3}

(

P = W / t

se).

Pascal ka base-unit form?

kg\cdotm^{- 1} \cdots^{- 2}

(

p = F / A

se).

Volt ka base-unit form?

kg\cdotm^{2} \cdots^{- 3} \cdotA^{- 1}

(

V = W / Q

se).

Ohm ka base-unit form?

kg\cdotm^{2} \cdots^{- 3} \cdotA^{- 2}

(

R = V / I

se).

Metre kis constant se define hota hai?

speed of light

c = 299792458 m/s

Kilogram kis constant se define hota hai (2019)?

Planck constant

h

Newton base unit hai ya derived?

Derived (

F = ma

se).

G

ka unit?

m^{3} kg^{- 1} s^{- 2}

°C aur K ka relation?

T_{° C} = T_{K} - 273.15

(degree ka size same, zero shift hua).

Connections

Dimensional Analysis — derived units consistency ke liye kaise check hote hain.
Significant Figures and Errors — har measured base/derived quantity mein uncertainty hoti hai.
Vectors and Scalars — units vector quantities ke magnitudes se attach hote hain.
Kinematics — velocity and acceleration — pehli jagah jahan derived units (m/s, m/s²) appear hote hain.
Newton's Laws of Motion — newton ke liye source equation.
Work, Energy and Power — joule aur watt ke liye source equations.

SI units — seven base units and all derived units

SI ki zaroorat KYU hai?

SAAT base quantities kya hain?

Base units ab KAISE define hote hain (2019 redefinition)

Derived units — recipe machine

Newton scratch se derive karo

Joule (energy) derive karo

Watt (power) derive karo

Pascal (pressure) derive karo

Coulomb aur volt derive karo

Worked examples

Common mistakes (steel-manned)

Active-recall flashcards

Connections

Concept Map

Deep Dive