MEASUREMENT AND UNITS
Dr. Auday K.
4/22/2024 DR. AUDAY K.A. 1
Measurement is a technique by means of which we attach a number to a
physical or chemical property as a result of comparing it, with a similar,
standard, quantity that has been adopted as a unit.Measurement
Measurement
units of
dimensional
quantities
Units dimensions
(Numerical value)
4/22/2024 DR. AUDAY K.A. 2
A number indicates "how much," but
the unit indicates "of what." The "of
what" is important when
communicating a quantity.Amount of Substance mole mol
UNIT PREFIXES
In addition to the basic SI units, we
can also use other units, such as
millimeters and nanoseconds, where
the prefixes milli- and nano- denote
various powers of ten. The measurement of physical or chemical quantities requires:
1) The standard or unit in which the quantity is measured.MEASUREMENTS
FUNDAMENTAL AND DERIVED UNITS
The physical quantities which do not
depend upon other quantities are called
fundamental quantities (in M.K.S.C.
system the fundamental quantities are
length, mass, time and charge).M.K.S.C. System: In this system the
units of length, mass, time and charge
are meter (m), kilogram (kg), second
(s) and charge (c) respectively.2) The numerical value representing the number of times the quantity
contains that unit.4/22/2024 DR. AUDAY K.A. 3
PRINCIPAL SYSTEMS OF UNITS
C.G.S. System: In this system the unit
of length is cm, that of mass is gm
and that of time is second.S.I. System (International System of
Units or Metric system): In this system
there are seven fundamental
quantities whose units and symbols
are given in a table.The units of physical or chemical
quantities which may be derived from
fundamental units are called derived
units.F.P.S. System (The British System): In
this system the unit of length, mass
and time are foot (f), pound (Ib) and
second (s) respectively.4/22/2024 DR. AUDAY K.A. 4
S.N. Fundamental
quantity
Unit Symbol
1.Luminous Intensity candela cd
6.The units of fundamental quantities are
called fundamental units.Length meter m
2.Mass kilogram kg
3.Temperature kelvin K
5.Electric Current ampere A
7.Time second s
4.