Noise in resistors: What is the type of noise generated due to random thermal agitation of charge carriers in a resistor?

Introduction / Context:
Noise is an unavoidable phenomenon in electronic circuits. Resistors generate a specific type of noise due to the random motion of electrons caused by thermal energy.

Given Data / Assumptions:

• Resistor at a finite temperature T.
• Noise voltage measured across its terminals.

Concept / Approach:

Thermal noise, also called Johnson or Nyquist noise, is proportional to the resistor value, temperature, and measurement bandwidth. Its power spectral density is uniform (white) over practical frequency ranges.

Step-by-Step Solution:

Verification / Alternative check:

Noise spectrum of a resistor shows flat (white) characteristic, confirming thermal noise is the correct answer.

Why Other Options Are Wrong:

• Partition noise: occurs in current division at semiconductor junctions.
• White noise: describes spectrum shape, but specific origin here is thermal.
• Shot noise: occurs in semiconductor diodes and vacuum tubes.
• Impulse noise: external transient disturbances, not inherent to resistors.

Common Pitfalls:

• Confusing white noise with thermal noise; while thermal noise is white, the correct physical term here is thermal noise.

Final Answer:

Thermal noise.