But that would introduce more complexity (polarity, biasing, etc) that would distract from the initial purpose. With a relay they should only learn how connecti

But that would introduce more complexity (polarity, biasing, etc) that would distract from the initial purpose. With a relay they should only learn how connecting a battery to pins 1 and 2 closes the contacts on 3 and 4. Using relays with more throws they can also learn the basics of logic gates, flip flops, etc. I believe that relays still have a place for educational purposes.