What happens when the circuit is turned off, creating an open circuit?
• Tell the students they will use a simple circuit as a guide to build a sensor to detect rain. • The simple detector they will use will be two strips of metal with a very narrow gap between them. When raindrops fall on and bridge the gap, they will complete (close) the circuit, turning on the light. Image to right: This shows a simple circuit with a sensor. Credit: NASA • Discuss procedure and safety instructions with students. • To test the circuits, spray them with a spray bottle. (BE CAREFUL TO ONLY SPRAY THE SENSOR!) • If the wood is absorbing the water, slip a thin piece of plastic underneath the metal strips. • To make sure the connections on the circuit are working correctly, use a paper clip to bridge the gap between the pieces of foil. This should close the circuit and cause the light to glow. Discussion/Wrap-up • After cleanup, discuss the activity/demonstration. • Brainstorm ideas of where this simple sensor could be useful. What could you replace the light with to make it
