Feynman Lectures Simplified 2A

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Making the Wonders of our Universe

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Robert L. Piccioni, Ph.D.

Feynman Lectures

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2A: Maxwell's Equations
and Electrostatics

Feynman Simplified 2A covers the first quarter of Volume 2, the freshman course, of The Feynman Lectures on Physics. The topics we explore include:
  • Maxwell’s Equations of Electromagnetism
  • Algebra & Calculus of Vector Fields
  • Gauss’ & Stokes’ Theorems
  • Electrostatics with Conductors & Dielectrics
  • Electrostatic Energy
  • Electricity in the Atmosphere
  • Why The Same Equations Appear Throughout Physics

Vector Fields

Another example of a vector field is heat flow. The figure below depicts heat flowing from a hot spot (white circle) above an isothermal plane (gray area at bottom). The boxed region of the main image is enlarged at the right.

Heat flow

The vector h indicates heat passing a selected point. Two planes (shown as gray bars) have areas A1 and A2. As the figure indicates, A1 is perpendicular to h but A2 is not. We wish to know the amount of heat flowing through each plane. The vector n is a unit vector normal to plane A22. Unit vectors have length 1.

We will define h in terms of the amount of thermal energy passing a selected point per unit time per unit area. We first define a surface that is perpendicular to h that has an infinitesimal area ΔA. We also define ΔJ to be the amount of thermal energy passing through ΔA per unit time. The equation for h is:

h = (ΔJ/ΔA) eh

Here eh is a unit vector in the h direction.