Does average power of cosine being zero mean we don't consume power to generate it?

The average power of cosine is zero. Does it mean that you dont consume any power to generate a cosine signal?

Re: power of cosine

Hi,
I think u've to correct u'r question.Its a bit ambiguous.However, my answer is Average signal power is calculated based on the amplitude of the signal irrespective of sine or cosine.
For ex., if the signal is represented as Acos2Πfmt, then its average signal power would be A²/2.
Regards
Bhanumurthy.

Re: power of cosine

The average power of Sin and Cos signals is 0.5.

power of cosine

The average power of sin is "0". The rms
power is A/sqr(2)=0.707 A.

power of cosine

Oh yeah you are right, it is 1/2. thanks everyone

Re: power of cosine

Well. Let’s check it, my friends. Of course, for circular functions Sin(wt) and Cos(wt) the areas under positive and negative halves of period are equal and of the opposite signs (if area can be negative), hence total value is zero. Therefore, mathematically the average (mean) value for the whole period is zero and here you are right. But electrical engineers are not mathematicians, their horizon must be wider and more close to the real life. What does it mean for this particular case? Let’s see. First of all, power is not a vector it is scalar. It has no sign or phase. Moreover, it is not real physical phenomenon, it is just artificially created tool for describing some real electrical processes. The initial question was about the amount of the energy that exchanges for one Cosine period. Definitely, it cannot be zero or it will be in contrary with the first law of thermodynamics. Because power is not more than artificial tool, we must use the absolute value in order to get the actual rate of the speed of energy exchange into the circuit. Electrical engineers usually call this rate as power (Watt=Joule/second).

It is not difficult to show that mean (or active as it more often called) power will be equal to U*I*Cos(phi). Here U and I are the RMS values for voltage and current and Cos(phi) we should consider equal to unit (or phi=0 degrees) because for our discussion we are talking about pure Cosine signal without any phase considerations. I think that now it is clear that this simple formula will provide resulting coefficient of 0.5.

This is simple material that usually studied on the first or second semester of electrical theory course and it is easy to check with any available textbook.

power of cosine

actully we use to talk about its rms value instead of average value that is amplitude/sqrt(2),this is special case of sin and cosine

Re: power of cosine

The initial question was about the average power. RMS is probably easier because it is used every day for electrical engineering tasks. Mean power is not so popular as RMS, but used a lot.