The Vector Potential: Feynman's Physics Explained

Feynman Vol II9-10

Just as the electric field comes from a voltage, the magnetic field can be derived from a 'vector potential.' Is it a real field or just a math convenience? In classical physics you could argue either way, but quantum mechanics settles it: it is real. The Aharonov-Bohm effect shows an electron can be affected by the vector potential even where the magnetic field is zero, shifting the phase of its wave. The vector potential is more fundamental than the magnetic field itself.

The big idea

The vector potential is not just math — quantum experiments prove it's real.

Think about it

How can something with no magnetic field present still change how an electron behaves?

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