does dc supply hav harmonics?

Answer 1

DC, or direct current is supposed to be pretty much a flat line deal. There should be no harmonics, but in truth, there can be and often are.

One cause is that the power supply may put some ripple onto the voltage, causing it to rise and fall somewhat, but the + side still stays more + than the - side.

There can be some low voltage alternating current superimposed on the DC. As long as the voltages do not reverse, it is still dc so a 20 v AC on a 100vdc will still be dc, but will vary from 80 to 120 volts.

The other thing that can happen is the potential of both the + and - might stay the same voltage apart, but they may vary compared to a ground voltage. This has been known to cause some serious problems when it is not properly anticipated.

You may also get a little back emf from a motor or other electronic device which makes one pole or another or both vary a bit.

Your electronic equipment will pick that up and can easily have problems with it. Speakers might hum.

So, the long and short of it is that your answer is yes. DC can have harmonics. In fact, unless great care is taken to eliminate them, it does.

Answer 2

pure dc has no harmonic but when you switch that and make the pulse wave you have made harmonic
when you make dc by ac wave you can not find pure dc and there is some ripple that they are in Small range and there is many harmonic but their harmonics are very small
if you use the battery when your load has been change the voltage of battery will be change and make some noise in dc and make some harmonic in that wave
as you know they are so smaller than the reference voltage but there is

Answer 3

Pure DC doesn't have anything else. On an osciloscope it should be just a boring flat line.

Answer 4

no but yes its possible