
I
t’s easy to build a circuit that responds to
metal in the environment, and this experiment
will show you how. Initially, you’ll find that
the circuit reacts when you place an object
such as a teaspoon in the center of a large-
diameter coil of wire. After completing this test
successfully, you’ll be able to modify the coil so
that it can detect coins in someone’s pocket. This
demonstrates how a coil generates a magnetic ...