Question

Thermal noise is generated in
(A) transistors and diodes
(B) resistors
(C) copper wire
(D) all of the above

Answer 1

Thermal noise is present in all electrical circuits. It is caused especially by all the components of any electronic circuits. So any types of transistor, diode, resistor, or copper wire are all parts of the electronic circuit and hence all of them produce thermal noise.

Complete step by step answer:
Thermal noise is also known as Johnson-Nyquist noise and electronic circuits are a major source of thermal noise. It is always present in electronic circuits. The thermal noise is generally caused due to the thermal agitation of the charge carriers or the electrons at equilibrium inside an electrical conductor irrespective of the applied voltage. The thermal noise increases with the increase in temperature. So many sensitive pieces of the equipment are cooled to a lower temperature to reduce this thermal noise in them.
All the components of an electronic circuit can produce thermal noise.
In the question, the options given to us are transistors and diodes, resistors, and copper wire. All of these components are the part of an electronic circuit and since thermal noise is always present in an electrical circuit so thermal noise is generated in each of these components.
Therefore the correct answer is option (D).

Note:
The thermal noise in the electronic elements can be caused due to the thermal agitation of electrons in it. The magnitude of thermal noise is directly proportional to the temperature of the surroundings. The thermal noise appears regardless of the applied voltage as the charge carriers vibrate due to the temperature. The noise can affect both the analogue and the digital signals.