Power Measurement – Watts , dBm and conversion
Most of us know that Watts is a unit of expressing power or the amount of the work done per unit of time. Electrically, One watt is defined as the amount of work done when one ampere of current is flowing through an Electric Potentiall difference of 1 Ampere.
In other words
P = VxA
If V is the voltage difference between a resistor of value R, then the wattage accross the resistor is given by
P = V*V /R
Example :- Find the wattage consumption accross a bulb of resistance 50 Ohm, if the voltage of 100 Volt is applied accross it.
Answer :- The wattage consumption is given by
P = V*V / R
V = 100 V
R = 50 Ohms,
So, P = 100 x 100 / 50
= 200 Watts
Many electricity companies report their power generation capacity in Megawatts. One megawatt is equal to 1 million watts.
RF and other electric design engineers use another unit of power consumption. It is a logarithmic measurement. Here is the formula to convert a power P into dBm
P(dBm) = 10 log10(p/p0)
P is the power in watts and P(dBm) is the power in dBm. Here p0 isequal to 1mW or 1×10-3 Watts. You may also use some online calculators to Calculate dBm from watts and vice versa.
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