Cap and copper bridge: what moves when you pressTwo contact posts: the gap the bridge closesA push button wired in a loop with a 1.5 V cell and a small bulb. A spring holds the copper bridge 7 px above two contact posts, so no current can flow. Press the cap and the bridge lands on both posts, the loop closes, and about 0.3 A lights the bulb. Let go and the spring lifts the bridge off again.