Electronics

Capacitor

Every charge is a ball you can count. Drive the source by hand and watch electrons get dragged off one plate, around the circuit and onto the other, until the field they build pushes back exactly as hard as you push.

Each ball is a real packet of charge; the number on the plates is exactly Q divided by that packet

Charge on the plates—

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Source

Drive it yourself 0.0 V

drag me up and down

Switch

Frequency —

slowfast

Resistor R 10 kΩ

100 Ω1 MΩ

Plate area A 1.00 m²

Plate gap d 10 µm

Dielectric κ 1.0

vacuumceramic

Time rate 1.0×

Draw a field line for every pair

Values

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What to observe

Drive the source up by hand. Electrons are dragged off the top plate, round the wire and onto the bottom one: nothing crosses the gap. Once the plates catch up with the source the balls stop, because current flows only while the charge is changing.
Close the switch on a battery. The current is set by the gap between the two markers on the voltage ladder, so it dies away as the capacitor catches up: an exponential with time constant τ = RC.
On AC the current peaks as the voltage crosses zero and vanishes at its peaks: it leads by a quarter cycle. Raise the frequency and the current grows, which is why a capacitor passes high frequencies and blocks DC.

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