Power Definition - Keysight V3500A User Manual

4 RF Measurement Basics

Power Definition

82
In electrical circuits, power delivered to an electrical load
can be defined as:
where
P is the delivered power.
V is the voltage applied to the load.
R is the resistance of the load.
When the power is in the form of an AC waveform, a more
complex definition is needed. The cyclic power from the AC
waveform varies with time. Although the power of an AC
waveform delivered at a specific time can still be defined
using the above formula, this does not adequately describe
the AC waveform power delivered to a load. Power of an AC
waveform delivered to an electrical load is equal to the
mean power delivered over the course of one cycle of the
sinusoidal waveform defined by:
T
∫
(
P =
0
where
T is the period of the AC waveform.
Evaluating the integral, we can reduce this expression to:
where
V is known as the root mean square (RMS) voltage of
0
the sinusoid.
2
V
----- -
P =
R
( ( ) T ⁄
V cos 2Πt
peak
2
V
0
--------
P =
R
2
) ) R ⁄ t d
V3500A User's Guide