Cut about 2 feet of bell wire and strip about an inch of plastic from each end. Wrap the wire around a wooden dowel rod a half-inch to an inch thick. Any thicker and the wire tube will allow for too much error; any narrower and the tube won’t be large enough for anything to pass through it later. Leave about 6 inches of loose wire at either end of the coil.

Slide the coil from the dowel rod and set the dowel aside. Turn your wooden box upside-down so you have a flat surface to work on. Roll a small snake of modeling clay and press it to the side of your D-cell battery. Press the clay on the battery to the wooden box to secure it. Use more modeling clay to secure your wire coil to the box, making sure that the loose wire ends can easily reach the battery.

Tape one wire end to the negative or flat battery terminal with duct tape. Leave the other one loose. Place a small bell or gong right next to one end of the wire coil and place the iron rod in the other end of the coil. A hand-held bell or a very small gong on a frame should work. Make sure part of the bell sits directly in front of the opening in the wire coil.

Touch the free wire to the positive or raised terminal of the battery. The wire coil should draw the iron rod in so it strikes the gong or bell. This is how your doorbell works. A wire coil creates a magnetic field that pulls in a rod to strike a chime.