Basics of the International System of Units
(1) Time - Second (s): -
In the System of International Units, the second is the unit of time. The duration of the radiation corresponding to the transition between the two HFS levels of the Caeslum-133 atom's ground state is 9,192,631,770 periods.
(2) Ampere (A) – Electric Current:-
In the System of International Units, the ampere is the unit of electric current. In a vacuum, one ampere is defined as a continuous current that produces a force of 2×10-7 Newton per meter of length between two straight parallel conductors of infinite length and insignificant circular portions one metre apart.
(3) Kelvin (K) - Thermodynamic Temperature:-
The thermodynamic temperature unit in the International System of Units is kelvin The Kelvin scale temperature of the triple point of water is 1/273.16 of the Kelvin scale temperature.
(4) Candela - Luminous Intensity:-
In the System of International Units, the candela is the unit of light intensity. Candela is the luminous intensity in a particular direction of a source emitting monochromatic radiation with a frequency of 540×1012 hertz and a radiant intensity of 1/683 watt per unit solid angle in that direction.
(5) Substance Amount – Mole:-
In the System of International Units, a mole is a unit of substance amount. The number of elementary entities in a mole is the same as the number of atoms in exactly 12 grams of the isotope Carbon 12.
Some Other Basic Information of Physics
Dimension:-
The process in which derived quantities are represented into their fundamental quantities of a Physical quantity. The dimension of a Physical quantity is used to find the nature of Physical quantity. It is also used to check the equations. The dimension of Physical quantity can be obtained by their formulas. The dimension of a Physical quantity can be expressed in terms of length, mass and time.
Length = L Mass = M Time = T
Significant Figures:-
The reliable digits in a number which are known as with certainty and the last uncertain digits are known as Significant Figures.
Scalar Quantities:-
Physical quantities which can completely be specified by a number (magnitude) having an appropriate unit are known as "Scalar Quantities".
Scalar quantities do not need direction for their description. Scalar quantities are comparable only when they have the same physical dimensions. Two or more than two scalar quantities measured in the same system of units are equal if they have the same magnitude and sign. Scalar quantities are denoted by letters in ordinary type. Scalar quantities are added, subtracted, multiplied or divided by the simple rules of algebra.
Examples:-
Work, energy, electric flux, volume, refractive index, time, speed, electric potential, potential difference, viscosity, density, power, mass, distance, temperature, electric charge etc.
Vector Quantities:-
Physical quantities having both magnitude and direction with appropriate unit are known as "Vector Quantities².
We can't specify a vector quantity without mention of direction. Vector quantities are expressed by using Capital letters and bold letters with arrow sign.
such as:
Vector quantities can not be added, subtracted, multiplied or divided by the simple rules of algebra. Vector quantities added, subtracted, multiplied or divided by the rules of trigonometry and geometry.
Examples:-
Velocity, electric field intensity, acceleration, force, momentum, torque, displacement, electric current, weight, angular momentum etc.
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