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basic question about signals

bhuvanesh

Aug 29, 2013
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in general we are checking whether the signal is power signal or energy signal. What is the use of finding whether the signal is power or energy signal. Do we have any special characteristics for energy and power signal that will be usefull for further analyses.In a nutshell WHY DO WE WANT CARE THE SIGNAL IS POWER OR ENERGY .Thank you in advance
 

(*steve*)

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I'm not sure that assertion is correct.

It is a little confused because energy and power are related -- do you know the difference?
 

(*steve*)

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Are you talking about a signal which has a zero vs non-zero average power?

And please don't start three threads for what is essentially one question.
 

bhuvanesh

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do you know the difference?
i know the difference in general.why we have distinguished signal as power and energy signal.where we use this power and energy signals
 

bhuvanesh

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energy is the ability to do something and power is the energy delivered in unit time
 

KrisBlueNZ

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OK, and what is the difference between an "energy signal" and a "power signal"?

BTW do not start any other threads on this subject.
 

bhuvanesh

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Okay sorry for that. That is my problem, in electrical circuits we use power and energy terms often in many things like how much energy is dissipated in energy , so on and so forth but how do we use power signals and energy signals in signals and systems.
 

Harald Kapp

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This makes no sense. A sine signal is also periodic and by your definition therefore an energy signal.
 

bhuvanesh

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Take a keen look of what i have said " periodic signals are power signal and aperiodic signal(non-periodic signals) are energy signals.

power signal

if a signal have constant power mean it lost some energy if a signal have no power i.e P=0(energy signal) it mean there is no energy is lost since its not going to have for too much period(non periodic)

sine signal(current) through resistor dissipate its energy as heat but a periodic signal does not cause any energy dissipation

Am i making any sense now?
 

Harald Kapp

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I'm sorry, this is what your post looks like on my screen:
unbenannt-png.18846

As you can see, there is a space between "a" and "periodic", so I read " a periodic" instead of "aperiodic".

I still do not understand your explanation:
sine signal(current) through resistor dissipate its energy as heat but a periodic signal does not cause any energy dissipation
You need to be careful when typing, here again it reads "a periodic", not "aperiodic". Also, the statement is incorrect. An aperiodic signal also can dissipate energy. Take for example a battery operated torch. Clearly the signal is aperiodic: You turn the torch on and when the battery is exhasted, the torch turns off. There is no periodicty involved. Still the lamp has dissipated lots of energy for shining a light and, as a side effect, heating the lamp.
 

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bhuvanesh

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wow interesting ,first time ever i am arguing confidently with people having high rating.okay let change the perspective

" all periodic signals are power signals but all power signals need not to be periodic signal".This is very famous statement ,you must have heard it. In that case step signal is only signal which is power signal but still its aperiodic.

you know very well that voltage discharged from batter is step signal and its again power signal.so its dissipates the power .Now i concluded i think

There is no periodicty involved

yes there is no periodicity involved but we can take whatever the period we wan it to be,cant we(this is just what i think).so it become periodic
 

KrisBlueNZ

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"all periodic signals are power signals but all power signals need not to be periodic signal".This is very famous statement ,you must have heard it.
Who said it? And can you link to where it appears?

Also, please provide links to the material you have been learning about this from.
 

Harald Kapp

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I believe he's talking about this
Good find, Steve.

What is stated there makes sense if you take into consideration signals of infinite duration. I don't know what's the use for this assumption, but then again I'm not that deep into signal theory.
 
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