# Could I Replace My Phone Battery With a Parallel Plate Capacitor?

5 min readMay 26, 2024

The world runs on batteries — I think that’s essentially true. But is it possible to replace a battery with a parallel plate capacitor? Also, why would you want to do that? Well, the first reason is that it’s a fun physics problem. There is a second reason too. A parallel plate capacitor is literally just two metal plates. That’s much easier to build that a lithium ion battery. Right?

# Electric Field, Potential, and Parallel Plates

We need to start with some basic physics. Imagine that I have two parallel metal plates with an area (A) and separated by a distance (d) — with the distance very small compared to the size of the plates. One plate has an excess charge (Q) and the other plate has an equal and opposite charge (-Q).

If the plates are very close together (much closer than in the diagram) then it will produce a constant electric field (E). The magnitude of this electric field can be calculated as:

Since this electric field is constant, it’s fairly easy to calculate the change in potential (ΔV) going from the negative to positive plate.

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Physics faculty, science blogger of all things geek. Technical Consultant for CBS MacGyver and MythBusters. WIRED blogger.