Test Your Hand

Build a game that lets you test how steady your hand is, by moving a loop around a wire figure without touching the wire. This makes a fun activity, and demonstrates the fact that current can only flow if there is a closed circuit. We give complete instructions for building the device.

Materials Needed: shoebox tape 1 metre of florist's wire (or other bare wire) 1/2 metre insulated wire

9v battery flashlight bulb (or small buzzer) ballpoint pen wire cutters

Step 1: Use the ballpoint pen to poke three holes in the lid of the shoebox, as shown.

Step 2: Snip off about 2 cm of the insulated wire and put it aside for later. Bare both ends of the remaining wire. Now fashion a small loop out of a short piece of the florist's wire, and twist it onto one end of the insulated wire. Seal the join with tape.

The size of the loop will determine how easy or difficult it is to win the game; the smaller the loop, the harder it is to win. You can modify the size of the loop later if it proves to be the wrong size.

Step 3: Pass the wire through the single front hole in the box lid, as shown.

Step 4: Transform the remaining florist's wire into a series of bends; make sure that the bends aren't too close together, and that they don't touch. Make as many bends as you want. (The more bends there are, the harder the game is to win.) Pass the loop you made in step 3 onto the wire with the bends, and then insert the ends of this wire into the remaining two holes in the lid, as shown.

Step 5: Turn the lid over and tape down the end of the wire on the right.

Step 6: Make a hole in the left front side of the box and insert the lightbulb, as shown. Place the 9v battery in the box.

Note: The game is much more fun if you can find a buzzer to replace the lightbulb; wire it like the bulb is wired, as shown below.

Step 7: Now we'll show you how to connect the wires. In order for the game to work, electricity must flow from one terminal of the battery, in a closed path (called a circuit), back to the other terminal. Attach wire A to the shank of the bulb; twist it on tight and use tape to hold it. Now get that short piece of insulated wire we cut off at the start, bare both ends, and attach it to the bulb socket tip, and one battery terminal. (Use tape to attach it to the socket tip; if you know how to use a soldering iron, a little solder will hold it permanently in place). Finally, attach wire end B (this is the insulated wire with the loop) to the other battery terminal.

Now the game is ready to play. The object is to move the loop around the bends in the wire shape, from one end to the other, without letting the loop touch the wire. if the loop is very small, this can be very difficult to do! You'll know when you lose, because the lightbulb (or the buzzer) will come on! When this happens, it means the wire has made a complete circuit.