# Significance of the experiment

By measuring Johnson noise — the fluctuating voltage that arises due to the random walk motion of electrons in a resistor (even when current isn’t flowing through it) —- as a function of temperature and frequency “bandwidth”, we can determine Boltzmann’s constant $$k_B$$, the fundamental constant connecting temperature $$T$$ to energy $$k_B T$$.

By measuring Shot noise — the fluctuations in a measured current of electrons due to quantization of charge — we can determine the fundamental unit of charge $$e$$ (the charge on an electron).

Who would have thought you could discover fundamental physics from simple “noise?” That’s pretty neat!

# Conceptual Introduction

Please carefully read the Noise Fundamentals Introduction and the Conceptual Introduction to Noise Fundamentals that are available on the TeachSpin website.

# Questions for first lab class

1. how might you measure voltage fluctuations in a resistor without having current flowing through it?

2. why would voltage fluctuations increase with resistance?

3. why would voltage fluctuations decrease with temperature?

# Activities for first lab class

To plan out your first full lab, please review the description of Johnson Noise in (Melissinos 2003) on pages 122 - 133 and the TeachSpin Noise Fundamentals Lab Manual, Section 7: A Practical Guide to Johnson-noise measurements.