Also, an interesting oddity about relays and switches: many have a minimum current rating because some arcing is actually required, it burns off the oxidation l

Also, an interesting oddity about relays and switches: many have a minimum current rating because some arcing is actually required, it burns off the oxidation layers on their contacts. This is called "wet switching", if you use a wet-switching relay to toggle a control voltage with negligible current flowing on the line, you can drive the relay to death prematurely due to oxidation. The solution is to use a control current instead of a control voltage, but it has higher power consumption (on the bright side, better noise immunity). There are also specialized "dry-switching" relays to solve this problem, usually for test and measurements applications (but using them to switch live circuits causes the opposite problem - arcing will damage them).