2. Physics Department Diploma Engineering
Physics Department Diploma Engineering
Chapter-1
SI Units & Measurements
3. Physics Department Diploma Engineering
Definition of Units
• The standard used for the
measurements of any physical
quantity is called Unit.
• Examples:
1. Meter, foot, inch for length.
2. Kilogram, pound, gram for weight.
3. Second, minutes, hour for time.
4. Physics Department Diploma Engineering
Physical Quantity
• The physical quantities which do not
depend upon any other quantities for
measurement.
• Examples:
• Mass of a person is 65 kg
• Length of table is 3 m
• Temperature of room is 100 K
5. Physics Department Diploma Engineering
Types of Units
M.K.S SYSTEM
• It is based on meter, kilogram and second as the fundamental units of length,
mass and time.
C.G.S SYSTEM
• It is based on centimetre, gram and second as fundamental units of length, mass
and time.
F.P.S SYSTEM
• It is based on foot, pound and second as the fundamental units of length, mass
and time.
6. Physics Department Diploma Engineering
Seven Fundamental Quantities
Fundamental Quantities S.I Units Symbol
Length Meter m
Mass Kilogram kg
Temperature Kelvin K
Electric Current Ampere A
Time Seconds S
Luminous Intensity Candela cd
Amount Of Substance Mole mol
7. Physics Department Diploma Engineering
Types of Physical Quantity
Fundamental Quantities
• The physical quantities do not depend
on any other physical quantities for
their measurements are know physical
quantities.
• Examples:
1. Time,
2. Temperature,
3. Mass,
4. Length
Derived Quantities
• The physical quantities which depend
on one or more fundamental
quantities for their measurements
are known as derived quantities.
• Examples:
1. Speed,
2. Force,
3. Momentum
8. Physics Department Diploma Engineering
Types of Physical Quantity
Scalar Quantities
• Those physical quantity which possess
only magnitude and no direction in
space
• Examples :
1. Temperature,
2. Time,
3. Mass.
Vector Quantities
• Those physical quantity which
possess both magnitude and direction
in space.
• Examples :
1. Velocity,
2. Acceleration,
3. Force
9. Physics Department Diploma Engineering
Definitions of Basic Units of SI System
• Metre: Its defined in terms of standard wavelength of lights and is equal to
16507693.73 wavelength in vacuum of radiation corresponding to transition
between energy level 2𝑝10 and 5d⁵ of krypton 86 atom.
• Kilogram: The mass of 1 litre pure water at 40c.
• Seconds: It is defined as 9192631770 periods of radiation corresponding to
unperturbed transition between the hyper fine levels of ground state of atom of
caesium atom.
10. Physics Department Diploma Engineering
Definitions of Basic Units of SI System
• Ampere: An ampere is a unit of measure of the rate of electron flow or current in
an electrical conductor. one ampere of current represents one coulomb of
electrical charge (6.24 x 1018 charge carriers) moving past a specific point in one
second.
• Kelvin: On thermodynamics scale
1
273.6
th part of temperature of triple point of
water is defined to be 1 K.
• Candela: The luminous flux radiated by 1/600000 sq. meter surface of a perfectly
black body having 1.01325*105 N/m2 pressure and temperature corresponding to
melting point of platinum.
11. Physics Department Diploma Engineering
Vernier Calliper
• Length of any specimen can be
measure in terms of meter,
centimeter, millimetre with help of
foot rule.
• Vernier caliper is used to measure
length of any specimen which is less
than mm.
• Least Count (L.C): The smallest value
that can be measured by the
measuring instrument is called its
least count.
𝑳𝑪 =
𝑽𝒂𝒍𝒖𝒆 𝒐𝒇 𝒔𝒎𝒂𝒍𝒍𝒆𝒔𝒕 𝒅𝒊𝒗 𝒐𝒏 𝒎𝒂𝒊𝒏 𝒔𝒄𝒂𝒍𝒆
𝑵𝒐 𝒐𝒇 𝒅𝒊𝒗𝒊𝒔𝒊𝒐𝒏 𝒐𝒏 𝒗𝒆𝒓𝒏𝒊𝒆𝒓 𝒔𝒄𝒂𝒍𝒆
12. Physics Department Diploma Engineering
Error Detection in Vernier Calliper
Corrected reading =Actual reading –/+ Error
For A reading = 5.14 – 0.00 = 5.14
For B reading = 5.14 – 0.03 = 5.11
For C reading = 5.14 + 0.06 = 5.20
13. Physics Department Diploma Engineering
Screw Gauge
• It is used for measuring accurately
the diameter of a thin wire or the
thickness of a sheet of metal.
• It consists of a U-shaped frame fitted
with a screwed spindle which is
attached to a thimble.
• Parallel to the axis of the thimble, a
scale graduated in mm is engraved.
𝑳𝑪 =
𝑷𝒊𝒕𝒄𝒉
𝑵𝒐 𝒐𝒇 𝒅𝒊𝒗𝒊𝒔𝒊𝒐𝒏 𝒐𝒏 𝒄𝒊𝒓𝒄𝒖𝒍𝒂𝒓 𝒔𝒄𝒂𝒍𝒆
15. Physics Department Diploma Engineering
Significant Figures
• Represent the accuracy with which u know your values.
• Rules for determining the significant figures
• Only uncertain figures should be retained.
• The zero on left hand side of number are not significant.
• The zero on right hand side of number are significant.
• When number is round off, if last number is more or equal to 5 then last figure
increased by one or if last number is less than 5 then last figure remain as it.
• Example : show significant figures in following examples.
1 . 48956 = 5
2 . 0.0003 = 1
3 . 300000 = 6
16. Physics Department Diploma Engineering
Accuracy
• It is defined as closeness of a
measurement of accepted value for a
specific physical quantity.
• Examples:
• True value of mass = 25.67kg
• Mass measured by A = 25.61kg
• Mass measured by B = 25.65kg
• The measurement made by student B
is more accurate
17. Physics Department Diploma Engineering
Precision
• It refers to the limit to which a
physical quantity is measured.
• Examples :
• Time measured by student A = 3.6s
• Time measured by student B = 3.69s
• Time measured by student C = 3.65s
• The measurement made by student C
is more precise.
19. Physics Department Diploma Engineering
Error
• Difference between the actual value of
a quantity and the value obtained by
measurement is called an error.
• Types of Error
1. Systematic Error
2. Random Error
20. Physics Department Diploma Engineering
Types of Error
Systematic Error : These
error arise due to flaws in
experimental system
Personal Error
Error arise due to fault
procedure made by person
while taking readings.
Instrumental Error
Error arise due to
instrument fault
Environmental Error
Error arise due to external
condition like temperature,
pressure
