Chapter 4, Problem 62A

Interpretation Introduction

Interpretation : Mullikan calculation of the mass of an electron is to be explained.

Concept Introduction : Mullikan performed tests to determine the magnitude of an electron's charge. Mullikan used two charged plates to suspend negatively charged oil droplets in his oil-drop experiment.

Answer to Problem 62A

Mullikan calculated the mass of an electron by the value of its charge and Thomson’s electron charge to mass ratio.

Explanation of Solution

Mullikan performed tests to determine the magnitude of an electron's charge.

Mullikan used two charged plates to suspend negatively charged oil droplets in his oil-drop experiment.

He then changed the voltage on the plates to see how this affected the droplets’ rate of fall. He found that the charge on each oil droplet a multiple of $1.6\times {10}^{-19}\text{coulomb}$ , meaning this must be the charge of an electron.

Mullikan calculates an electron’s mass by using the charge value and Thomson’s charge-to-mass ratio of an electron.

An electron has one unit of a negative charge, and its mass is 1/1840 the mass of a hydrogen atom.