Chapter-02
Definitions
1. Meter
The length of the path traveled by
light in vacuum in 1/299,792,458 of a second is known as meter.
Length is a fundamental unit used for
measurements of length, distance and height. It is equal to the distance
between two marks on a Platinum-Iridium bar kept at 0 C in International Bureau
of Weight and Measurements (IBWM) near Paris.
2.
Kilogram
The mass of a Platinum-Iridium
cylinder kept at 0 C in International Bureau of Weight and Measurements (IBWM)
near Paris is considered to be 1 kilogram.
Kilogram is a fundamental unit used
for measurements of mass.
3. Second
It is equal to the duration of
9,192,631,770 periods of radiation of Cesium-133 in ground state.
Fundamental
Units
The international system of units is
based on seven independent units known as Fundamental or Basic Units. These are
given below:
1. Meter (m):
length, distance, height (l)
2. Kilogram
(kg): mass (m)
3. Second
(s): time (t)
4. Ampere
(A): electric current (I)
5. Kelvin
(K): temperature (T)
6. Mole
(mol): amount of substance (n)
7. Candela
(cd): luminous intensity (Iv)
Derived Units
The units that require two or more
basic measurements of same units or different fundamental units for its
definition are called derived units.
1. Square
meter (m2): area (A)
2. Cubic
meter (m3): volume (V)
3. Hertz
(Hz): frequency (v)
4. Kilograms
per cubic meter (kg/m3): mass density (p)
5. Meter per
second m/s: speed
velocity (V)
6. Radians
per second (rad/s): angular velocity (w)
7. Meters
per second square (m/s2): acceleration (a)
8. Newton
(N) (kg.m/s2): force (F)
9. Pascal
(Pa) (N/m2): pressure (P)
10. Joule
(J)(N.m): work (W), energy(E), quantity of heat (q)
11. Watt (W)
(J/s): power (P)
12. Coulomb
(C) (A.s): quantity of electric charge (Q)
13. Volt (V)
(W/A): potential difference (V), electromotive force (E)
14. Ohm
(Omega): electric resistance (R)
15. Farad
(F)(A.s/V): capacitance (C)
16. Weber
(Wb)(V.s): magnetic flux (@)
17. Henry (H)
(V.s/A): inductance (E)
18. Volts per
meter (V/m): electric field strength (E)
19. Newton
per coulomb (N/C): electric field strength (E)
20. Tesla (T)
(Wb/m2): magnetic flux density (B)
21. Ampere
per meter (A/m): magnetic field strength (H)
22. Joules
per kilogram Kelvin: (J/kg.K) specific heat (Q)
Vernier Callipers
A vernier calipers is an instrument
that is used to measure the length, diameter and depth of solid substances
accurately up to 0.1mm. A vernier calipers has two scales, the main scale (MS)
and vernier scale (VS). The vernier scale (VS) slides over the main scale (MS).
Vernier
Count (VC)
The smallest measurement that can be
made with the help of a vernier calipers is known as least count of vernier
calipers or vernier count (VC). Least count of the vernier calipers is
calculated by
L.C = Value of Smallest Division of MS/Total Number of Divisions on VS
L.C = Value of Smallest Division of MS/Total Number of Divisions on VS
Micrometer Screw Gauge
A screw gauge is an instrument that
is used to measure thickness of a wire, glass, plastic and metal sheets
accurately up to 0.01mm. A micrometer screw gauge has two scales, the main scale
(MS) and the circular scale (CS). The circular scale rotates over the main
scale.
Least Count
(LC)
The smallest measurement that can be
made with the help of a screw gauge is known as least count of screw gauge.
Least count of the screw gauge is calculated by:
L.C = Pitch of the Screw / Total
number of divisions of CS
where pitch is the distance between two consecutive threads of the linear screw.
where pitch is the distance between two consecutive threads of the linear screw.
Physical
Balance
A physical balance is an instrument
that is used to find the mass of an object. Actually, it is the lever of the
first kind with equal arms.
Stop Watch
A stop watch is an instrument that is
used to measure accurately the time interval for any physical event. It can be
used to measure the fraction of a second.
Measuring
Cylinder
A measuring cylinder is a glass
cylinder of uniform area of cross section with a scale in cubic centimeter or
millimeter marked on it. It is used to measure the volume of a liquid.
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