# Electronic Circuits and Projects Forum

1. ## interference of signal and noise waves

Hi

Q1: In DC current electrons simply follow a 'smooth' path without any fluctuations and that's what direct non-alternating current is.

Now let me tell you what I think of AC current. As you can see in this diagram there are two terminals A and B. e(-) stands for electrons and arrows stand for their direction of motion. When electrons are moving toward left of the page, the current or voltage is +ve and when electrons are moving towards right of the page the current is -ve.

Each terminal, A and B, switches between +ve and -ve. When A is +ve, B is -ve. If the frequency of AC is 50 Hz then each terminal would switch between opposite polarities 100 times during one second. So, it is all about push and pull of electrons.

In a wire electronic current flows more like sound waves rather water waves. Isn't it so? So, would you define an alternating current a longitudinal wave? A longitudinal wave can also be shown as a sine wave as is shown here.

Q2: When two waves meet there is going to be interference. This applet is a good one to see this. For example, in this configuration both waves have same amplitude and are in phase which results in double amplitude. I hope everything is correct so far. Now we turn to the main question. As the figure shows noise wave is 'riding' the main signal wave. I'm having a lot of difficulty to picturize it. When a signal wave is superimposed with noise wave, we are going to get a new third wave, aren't we? So, technically speaking noise wave is not riding the signal wave. I think I will wait for your reply to this and then will move on with the next part of the question. Thank you for the help.

Regards
PG