# Effect of noise on a circuit

1. Jan 6, 2010

### Sahara

Hello,

I am trying to understand how noise affects the potential measured across a certain point of a circuit.
If we have two alternating voltage sources in a circuit, I understand that the "sum" of the potentials provided can affect the potential at the point of interest. However, I am having trouble understanding where this third form of potential comes from and how exactly it can change the resultant voltage waveform at the point of interest!

Let me know if this is unclear and thank you!

2. Jan 6, 2010

### waht

There is a lot of different kinds of noises. There is thermal noise due to random fluctuation of electrons, noise from outside interference, or noise generated by different circuits.

Which noise are you referring to in particular, or is this just a general question?

3. Jan 6, 2010

### Sahara

This is just a general question. I'm starting to learn about sensors, but I dont understand the physics behind how potential can be created from noise.

4. Jan 6, 2010

### ranger

Re: Effect of noise in a circuit

Your question seems a little vague. This third component (noise) can have lots of sources. Can you give a specific scenario?

5. Jan 6, 2010

### Sahara

Re: Effect of noise in a circuit

Well I just learnt that noise has an effect on the received signal. I'm not sure what this outside noise component comes from, I actually didn't even know there different categories of sources :S, but my question comes from a demonstration where a signal that is sent from a sender to a receiver is affected by this factor that was called noise.
And I was wondering how this "noise" can create a potential..
Sorry if it's unclear! i think I will read a bit more about it first to see if I can clarify more

6. Jan 7, 2010

### Staff: Mentor

welcome to the PF. I googled sensor noise tutorial, and got lots of good hits:

.

7. Jan 7, 2010

### Bob S

Re: Effect of noise in a circuit

Two possible noise sources are:
1) The quantization of charge in low currents (1 nanoamp = 6.25 electrons per nanosecond) creates Schottky noise in small signals.

2) Thermal fluctuations in resistors create a noise voltage. See
http://www.sengpielaudio.com/calculator-noise.htm

Also there is the plain old interference from other wireless transmitters and electrical equipment, and the CMB (cosmic microwave background).

Bob S

8. Jan 7, 2010

9. Jan 7, 2010