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VainVeinyVane OP t1_j641t7v wrote

OK. Got the answer. For anybody who stumbles upon this question and has the same question: Current is proportional to direction and concentration of charge, whereas Voltage is only proportional to concentration of charge.

So when the electrons "bounce" off the end of the end of the antenna (the wave is reflected), the NEGATIVE of the wave is reflected for current (since the direction reverses!), while the POSITIVE of the wave is reflected for the voltage.

For example:

if the wave is cos(wt-kx), the reflected traveling wave is -cos(wt+kx) for current, while the reflected wave for voltage is +cos(wt+kx).) The resulting standing waves formed are one with peaks at the ends for voltage, while the current's resulting standing wave has its peak at the center and nodes at the ends.

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The graph for current, cos(wt-kx) - cos(wt+kx) will be 2sin(wt)sin(t). This is a standing wave with nodes at the ends of the antenna.

However, the graph for voltage, cos(wt-kx)+cos(wt+kx) will be 2cos(wt)cos(kx). This is a standing wave with the node at the center of the antenna and peaks at the ends (90 degrees shifted from the current standing wave).

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Hope this helps!

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zutnoq t1_j656wje wrote

If you want a more hand wavy explanation I think the antenna is essentially acting as a giant capacitor (or rather one side of a capacitor) which would certainly explain the 90° phase difference between voltage and current as that is exactly what happens with a regular capacitor driven with AC (the exact opposite phase shift happens for an ideal inductor driven with AC).

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VainVeinyVane OP t1_j65y9rc wrote

can you explain how it acts like a capacitor lol I'm having a hard time wrapping my head around it.

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zutnoq t1_j67q8kj wrote

A capacitor is essentially two plates of metal separated by a layer of insulator. The antenna is acting like one of those plates of metal, the air is the insulator and (the) ground is acting as the other plate.

Edit: in this specific case the other arm of the antenna is the other plate, if that wasn't obvious.

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