I can't but think of this analogy: Transistors are like Judo. You can use them by keeping your feet firmly on the ground, then applying a small amount of energy

I can't but think of this analogy: Transistors are like Judo. You can use them by keeping your feet firmly on the ground, then applying a small amount of energy to a point (base current) you can control and use to your advantage a much bigger energy that comes from the opponent (collector current through the load).