SI Units of Measurement, Scientific Notation and Scientific Figures

What is a physical quantity?

A Physical Quantity is a quantity that can be measured.

Base quantity?

A quantity that does not depend on other quantities to be defined or determined.

Mole of a substance?

A mole of a substance contains Avogadro’s constant of elementary particles, a mole of a substance contains 6,02 × 10²³ basic particles

The reason we use SI units?

To create a standardisation and ensure that everyone uses the same system to be universally understood.

Length (l)

meter (m)

Mass (m)

kilogram (kg)

Time (t)

second (s)

Temperature (T)

Kelvin (K)

Electrical current (I)

ampere (A)

Potential difference (V)

volt (V)

Luminous Intensity (I)

candela (cd)

Number of chemical units (n)

mole (mol)

How many kelvin is 0C

273K

Distance

Distance is the path of length travelled by an object.

Luminous intensity

Luminous intensity is the brightness of light that an object emits in a certain direction.

Temperature

Temperature is a measure of the average kinetic energy of the atoms/particles/molecules of a substance.

pico (p)

10^-12

nano (n)

10^-9

micro (μ)

10^-6

milli (m)

10^-3

centi (c )

10^-2

deci (d)

10^-1

SI unit

10⁰

kilo (k)

10³

Mega (M)

10⁶

deka (da)

10¹

hecto (h)

10²

Giga (G)

10⁹

Tera (T)

10¹²

Direct Proportionality

Two quantities are directly proportional if, when one quantity is increased by a certain factor, the other quantity increases by the same factor.

x axis

independent variable

y axis

dependent variable

Characteristic of two quantities that are directly proportional

Straight line that passes through the origin

(Direct proportionality) y/x

= k (direct proportionality)

(Direct proportionality) k X y

= x (direct proportionality)

(Direct proportionality) y

∝x

Inverse Proportionality

Two quantities are inversely proportional if, when one quantity is increased by a certain factor, the other quantity decreases by the same factor.

(Inverse Proportionality) y X x

= k (inverse proportionality)

(Inverse Proportionality) y

= k/x (inverse proportionality)

(Inverse Proportionality) y

∝1/x

slope or gradient

= change in y / change in x

(Inverse Proportionality) y vs x

is a hyperbola / curve

(Inverse Proportionality) y vs 1/x

is a straight line