Transcript Chapter 1: Units and Dimensions  SI Mechanical Units – Fundamental Units • Length: meter (m) • Mass: kilogram (kg) • Time: second (s) – Derived Units • Meter.

Chapter 1: Units and
Dimensions

SI Mechanical Units
– Fundamental Units
• Length: meter (m)
• Mass: kilogram (kg)
• Time: second (s)
– Derived Units
• Meter Squared (m2)
• Liter
– Unit of Force
• Newton (N): the force which will give
a mass of 1 kilogram an acceleration
of 1 meter per second per second.
Force  m ass acceleration
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– Work (joule (J))
• The work done in moving a body is the
product of the force and the distance
through which the body is moved in
the direction of the force.
Work  Force Distance
• The joule is defined as the amount of
work done when a force of 1 newton
acts through a distance of 1 meter.
• The joule may also be termed a
newton-meter.
– Energy: the capacity for doing
work, joule (J)
– Power: the time rate of doing work
• If a certain amount of work W is to be
done in a time t, the power required is
Power 
Work
time
• The Watt is defined as the power
developed when 1 joule of work is
done in 1 second.
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
Scientific Notation and Metric
Prefixes
– Scientific Notation: very large or
very small numbers are
conveniently written as a number
multiplied by 10 raised to a power
– Metric Prefixes: a letter symbols
for the various multiples and
submultiples of 10
– Engineering Notation: Symbol,
e.g., T for tera, G for giga, M for
mega, and k for kilo.
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
SI Electrical Units
– Units of Current and Charge
• Ampere (A): the unit of electric current
and is defined as that constant current
which, when flowing in each of two
infinitely long parallel conductors 1
meter apart, exert a force of
2 107 newton per meter
of length of each conductor
• Coulomb (C) is defined as that charge
which passes a given point in a
conductor each second, when a current
of 1 ampere flows.
Amperes 
Coulombs
Seconds
1
6. 24  1018
 1. 602  1019 C
Q
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– Emf, Potential Difference, and
Voltage
• Volt (V): is the unit of electromotive
force (emf) and potential difference.
• The volt is defined as the potential
difference between two points on a
conductor carrying a constant current
of 1 ampere when the power dissipated
between these points is 1 watt.
1 eV 
1
J
6.24  1018
– Resistance and Conductance
• Ohm (): is defined as that resistance
which permits a current flow of 1
ampere when a potential difference of
1 volt is applied to the resistance.
• Conductance (G): is applied to the
reciprocal of resistance. The siemens
(S) is the unit of conductance.
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– Magnetic Flux and Flux Density
• Weber (Wb): is defined as the
magnetic flux which, linking a
single-turn coil, produces an emf of
1 V when the flux is reduced to zero
at a constant rate in 1 s
• Tesla (T): is the flux density in a
magnetic field when 1 weber of flux
occurs in a plane of 1 square meter;
i.e., 1 Wb/m2
– Inductance
• The inductance of a circuit is 1
henry (H) when an emf of 1 volt is
induced by the current changing at
the rate of 1 A/s.
– Capacitance
• The farad (F): is the capacitance of a
capacitor that contain a charge of 1
coulomb when the potential
difference between its terminals is 1
volt
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
SI Temperature Scales
– Celsius scale; has 100 equal
divisions (or degrees)
– Kelvin scale (absolute scale)
• Commences at absolute zero
temperature (-273.15oC)

Dimensions
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
Standards
– International Standards
• Defined by international agreements
and maintained at the International
Bureau of Weights and Measures in
France
– Primary Standards
• Maintained at institutions in various
countries around the world
• Main function: Checking the
accuracy of secondary standards
– Secondary Standards
• Employed in industry as references
for calibrating high-accuracy
equipment and components and for
verifying the accuracy of working
standards
– Working Standards
• Used as measurement references on
a day-to-day basis in all electronics
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