Page:The Meaning of Relativity - Albert Einstein (1922).djvu/59

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.
SPECIAL RELATIVITY
47

There is, therefore, a four-dimensional vector of force per unit volume, whose first three components, , are the ponderomotive force components per unit volume, and whose fourth component is the rate of working of the field per unit volume, multiplied by .

A comparison of (36) and (35) shows that the theory of relativity formally unites the ponderomotive force of the electric field, , and the Biot-Savart or Lorentz force .