# Energy and power signals

1. Jan 24, 2017

### LLT71

in terms of calculating energy and power, why don't we use absolute value of signal and then integrate it from -inf to +inf instead of squaring it and then integrating it over -inf to +inf?
for example ∫|sinx|dx (from -inf to +inf) will give you, relatively speaking, the same answer as ∫[sinx]^2dx (from -inf to +inf).

what is physical significance of determining if signal is power or energy one? what those two quantities tell you besides if signal is periodic/non-periodic?

2. Jan 24, 2017

### Staff: Mentor

Are you integrating voltage, current or power?

3. Jan 24, 2017

### LLT71

please sorry in advance for my ignorance! in my Signal Processing textbook it says that for every continuous signal we define energy of signal as ∫|[x(y)^2]|dx so, since I'm new at this I presume it stands for "any signal".

4. Jan 24, 2017

### sophiecentaur

A couple of points here. If you integrate (+-∞) an AC Voltage or Current signal, the result is Zero.
The reason for using Mean Square or Root Mean Square is that you very seldom have both V and I signals available. RMS gives you the (Average) Power that your Voltage waveform will dissipate in a resistive load without Integrating VI (which is not zero because both signs change at the same time to produce positives for each half of the cycle).
Power = V2R or I2R, whichever you choose or can measure.
We normally deal with Power, in these cases and that is the Average over a specific time (a number of whole cycles of the waveform ). So your Integration is not +-∞.