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Unformatted text preview: difference and electromotive force) is the difference of
electric potential between two points of a conductor
carrying a constant current of one ampere, when the
power dissipated between these points is equal to one
watt (W = J/s) The watt is the power that represents a
rate of energy transfer of one joule per second.
weber (Wb = V.s) The weber is the magnetic flux that,
linking a circuit of one turn, produces in it an electromotive force of one volt as it is reduced to zero at a
uniform rate in one second.
C.2.5 Units in Use with SI Time The SI unit of time is the second. This unit is preferred and should be used if practical, particularly when
technical calculations are involved. In cases where time
relates to life customs or calendar cycles, the minute,
hour, day and other calendar units may be necessary.
For example, vehicle speed will normally be expressed
in kilometers per hour.
minute (min) 1 min = 60 s
hour (h) 1 h = 60 min = 3600 sec
day (d) 1 d = 24 h = 86 400 sec
week, month, etc.
Plane angle The SI unit for plane angle is the radian.
Use of the degree and its decimal submultiples is
permissible when the radian is not a convenient unit.
Use of the minute and second is discouraged except for
special fields such as astronomy and cartography. Volume The SI unit of volume is the cubic meter. This
unit, or one of the regularly formed multiples such as the
cubic centimeter, is preferred. The special name liter
has been approved for the cubic decimeter, but use of
this unit is restricted to volumetric capacity, dry
measure, and measure of fluids (both liquids and
gases). No prefix other than milli- or micro- should be
used with liter.
Mass The SI unit of mass is the kilogram. This unit, or
one of the multiples formed by attaching an SI prefix to
gram (g), is preferred for all applications. The
megagram (Mg) is the appropriate unit for measuring
large masses such as have been expressed in tons.
However, the name ton has been given to several large
mass units that are widely used in commerce and
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