Which of the following is not a primary source of external noise?

Which of the following is not a primary source of external noise? Correct Answer Thermal noise

NOISE:

• Noise is an undesirable product of the electronic devices and components and, more noise results from intentional economies of manufacture and design time.
• The measure of the noise performance of a circuit is the noise figure or noise factor. Noise figure is a comparison between the output signal to noise ratio and the thermal noise of the input signal.

Noise in communication systems is generally divided into two categories-

i) External noise like atmospheric noise, industrial noise solar noise, and cosmic noise.

ii) Internal noise like shot noise, thermal noise, low and high-frequency noise.

Internal and external noises are the main source of noise in the receiver. 

Thermal noise:

• It is also called Johnson-Nyquist noise
• It arises due to thermal agitation of electrons in a conductor material when the temperature is increased above absolute zero and it is also called thermal agitation noise
• It is distributed across the entire frequency spectrum range so it is also called white noise
• Thermal noise is generally observed in the passive component like R, L & C due to the random movement of charge carriers electrons.
• Random noise power is

Pn = KTB

Where,

K = Boltz man's constant

T = temperature

B = Bandwidth over which noise is measured