Could make a paper tube that is analogous to a wire. Then, chuck marbles through the paper tube one by one at different time intervals. If you increase the time interval, it is equivalent to having less charge flowing through for a period of time, and hence lower current as current is the rate of change of charge with respect to time.
If you decrease the time interval to chuck the marbles in, then you can say that current was increased.
Now, place this tube along a bench. Make sure that the tube is angled downwards and make some sort of bridge so that the paper is not supported in the middle.
If you decrease the time interval between placing each marble in the tube and letting it roll downwards, then you increase the "current". Eventually, the paper tube that is not supported in the middle will break if there are too many marbles and hence, it will break due to a large "current". The paper not being supported by anything is effectively a fuse.
To model a switch, you can have the tube diverge and move to another path, then have a blocking material that blocks the marbles from coming out of the tube and spilling everywhere. You should probably use a metal for this blocker. When you diverge the circuit and block the marbles from coming out, the "switch" you have just made is "opened". Then when you put the tube back so that the marbles can go to the other end (and take out the blocker), then the "switch" is "closed".
Another thing you can do, for RCD protection you can use magnets. This will depend on how you set it up and you will need to be pretty creative.