The power of Ohm’s Law

Ohm (never one to sit around twiddling his thumbs) also expressed that
power is related to voltage and current using this equation:
P = V x I; or power = voltage x current
You can use this equation to calculate the power consumed by the buzzer in
the previous section:
P = 12 volts x 0.006 amps = 0.072 watts which is 72 milliwatts (or 72 mW)
What if you don’t know the voltage? You can use another trick from algebra.
(And you thought Mrs. Whatsit wasted your time in Algebra 101 all those years
ago!) Because V = I x R, you can substitute I x R into this equation, giving you
P = (I)(I) x R; or power = current squared x resistance
You can also use algebra to rearrange the equation for power to show how
you can calculate resistance, voltage, and current if you know power and any
one of these parameters.
Do you really hate algebra? Did Mrs. Whatsit fail you those many years ago?
You’re probably happy to hear that online calculators can make these calculations
much easier. Try searching on www.google.com using the keyword
phrase “Ohm’s Law Calculator”