Although many people have doorbells in their homes, most are electric doorbells with speakers and sound effects. Very few doorbells use chimes and hammers anymore. The first doorbells used simple electromagnets to pull a hammer toward a chime. The hammer would strike the chime with some force and make a loud chiming sound. However, you can make one of these old-style doorbells at home. Help your child make a doorbell as a science project, or use it as your own science demonstration.
- Skill level:
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Things you need
- Coated copper wire
- 1-inch thick dowel
- Wire snips
- Wire strippers
- 6-volt battery
- Electrical tape
- Acid-free cardboard box
- Hot glue
- Large iron or steel nail
- Miniature gong
Wrap the dowel with copper wire in close-together coils. The ending coil should be about 4 inches long with 6 inches of wire trailing off the dowel; use snips to cut the wire. Unroll the spool attached to the other end of the wire so you have another 6-inch tail. Snip the wire here, too.
Strip the coating from the last inch of each copper wire tail. Stand an acid-free cardboard box (like a shoebox) on its side and slide your 6-volt battery inside. Run a bead of hot glue across the centre of the top side of the box. Press your copper wire coil into the glue.
Bend the wire tails inside the box, taping one of the tails to the negative terminal of the battery. Let the other tail hang free, but make sure it reaches the positive battery terminal.
Set the miniature gong to the left open end of the copper coil. Lay the head of the large nail in the other opening. Your miniature gong is just what it sounds like; a small, Chinese-style gong in a free-standing frame. They're usually about the size of your palm.
Touch the free trailing wire tail to the battery's positive terminal. The resulting electric field inside the tube should pull the nail through the tube and make it bang into the gong. Your doorbell is complete.
Tips and warnings
- You can use anything that make lots of noise for a gong. A Tibetan singing bowl would work well, as would a small bell suspended from a frame.
- Paint the cardboard box to create a conversation piece or to give a conversation piece a neater look.
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