Is it possible to explain a transistor (or vacuum tube or relay) using a marble-based switch for students?

Question

In Japan I saw a simulation of internet based communication in the The National Museum of Emerging Science and Innovation (Miraikan). It attempted to replicate ascii characters moving along a 8 part wire using combinations of marbles rolling along.

I've just finished reading Charles Petzold's book, Code: The Hidden Language of Computer Hardware and Software. In it Charles explains building relays into gates, gates into logic components, and logic components into computing machines.

I wondered if a mechanism existed that simulated a switch using marbles.

My question is: Is it possible to explain a transistor (or vacuum tube or relay) using a marble-based switch for students?

Answer 1

I'd be thinking of something like this:

The top hopper contains blue marbles (so you can see where things come from). A spring loaded flap prevents anything falling.

Drop a red marble into 'base' tube ( = small base current) - it opens the flap momentarily, marbles drop from the 'collector' hopper and the red ('base' marble) and blue ('collector') marbles accumulate in "emitter' container below.

Flap then closes due to spring action (that's the tricky mechanical part).

The gain of the 'transistor' is then determined by how many blue marbles fell for a single red marble. Analogy gain = collector current/base current.

We also can see Kirchoff's current law in action -

the number of 'emitter' marbles = number of collector marbles + the base marble

or the analogy emitter current = base current + collector current

Hope this gives you some ideas.