Challenge HN: Convince an ancient Greek that you are from the future

I think that my goal would be to demonstrate electrical devices starting with simple components and scale up progressively as people become more convinced.

As a starting point with minimal material requirements, I would build Faraday's rotating motor using: coins made of two different base metals and cloth soaked in saltwater for a battery, a lodestone as a natural permanent magnet, and wire or thin beaten sheet of any non-ferrous metal with a saltwater pool. Demonstrating continuous electromagnetic motion will hopefully be enough to secure some patience to request materials for further construction.

Radio demonstration would need to settle for morse code transmission because all of the components necessary for a basic radio receiver/transmitter are simple except for an amplifier. The leap in difficulty to construct a triode vacuum tube amplifier seems too far to expect to progress to voice transmission quickly. I would hope that a local ruler would understand the value after seeing a wireless telegraph in action.

The priorities from here would be to use the accumulated prestige to request smiths to make copper wire, to requisition the more exotic but already known sulfuric acid, construct lead-acid batteries, and short them through a copper coil containing an iron bar to make strong permanent magnets for use in practical motors and generators.

Once you get a bit of support, you can progress as far as needed through nineteenth century electrical development until they are convinced.

Long division.

> build a small furnace with an exhaust that can shift a propellor shaft.

The Aeolipile was described shortly before the common era, but it took another 1600 years before anyone could build a steam engine capable of real work.

https://en.wikipedia.org/wiki/Aeolipile

I was going to suggest that too.