What
is the Unit of Power?
Unit of power is the watt,
which is named in honor of the English scientist
JAMES
WATT. By knowing the voltage and current
throughout a circuit, we may monitor energy
exchanges.
Passive Sign Convention
Current direction and voltage
polarity play a major role in determining
the sign of power. The voltage polarity
and current direction must conform with
those in Figure 6.1 in order for the power
to have a positive sign. This is known as
the passive sign convention.
With a current arrow placed by the upper
lead, directed to the right, an amount of
power p
= vi
is being absorbed by the element
to the right. It is also correct to say
that a power p
= vi
is being delivered to the element.
Figure 6.1 Power
absorbed by an element
Energy and Power
Energy
is the capacity to do work. It is measured
in joules (J). The energy exchanged in a
period of time t1<
t < t2 can be calculated by
integration
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