Make an Electroscope

An electroscope is a device that is used to detect static electricity. Static electricity is the build-up of an electric charge on the surface of an object. Electrons transfer from surfaces with high charge, to a surface with less charge. An electroscope can detect the transfer of electrons and give you an idea of how charged something is. You can make a simple electroscope out of household items and figure out how much static electricity is around your home! Adult supervision is recommended for some of the required steps.

Steps

Making a Foil Leaf Electroscope

1. Gather your materials. Most of these materials are household items that are easy to find. To make this electroscope you will need:
   • A clear jar (glass or plastic)
   • The jar lid
   • 14 gauge copper wire (can be obtained at any local hardware or home improvement store)
   • A plastic straw
   • Scissors
   • A hot glue gun (can be purchased at any craft store)
   • Aluminum foil
   • Wire cutters
   • Pliers
   • A ruler
   • A hammer
   • Tape
   • A balloon
2. Cut the copper wire to {{safesubst:#invoke:convert|convert}} and the plastic straw to {{safesubst:#invoke:convert|convert}}. Ask for adult assistance to cut the copper wire with wire cutters. The straw can simply be cut with scissors. Measure with the ruler and cut to the desired length.
   • When cutting the wire, sometimes pieces will snap away during the cut. It is recommended to wear eye protection during this step.
3. Punch a hole in the lid of the jar. The hole in the lid needs to be large enough for the straw to fit through. Ask an adult for help with this step. Position a nail or punch in the center of the jar lid and hammer through until you have a hole of appropriate size.
   • Take caution with this step. It is recommended to wear eye protection in case bits of plastic fly during the hammering process.
   • If you punch the hole too big, simply add more hot glue in the next step to secure the straw in place.
4. Secure the straw to the lid with hot glue. Insert the straw into the hole until half of the straw is above and below the lid. With the hot glue gun, secure the straw in place by gluing all along the edges of the straw and hole.
   • Ask for adult supervision with the hot glue gun as it is very hot and can cause burns.
5. Twist the top {{safesubst:#invoke:convert|convert}} of the copper wire into a spiral. This spiral is important because it allows electrons to be transferred from an object to the electroscope. More surface area means more electron transfer and a bigger response from the electroscope.
   • Hold on to one end of the wire with the pliers and twist it around to form the spiral shape.
   • Make a loose spiral with some space between each curl.
6. Insert the copper into the straw and make a hook {{safesubst:#invoke:convert|convert}} long. Insert the straight end of the wire into the straw so that the spiral is on the top side of the lid. With the last inch of the wire, shape the straight end into a hook. This hook will hold the foil leaves in place.
   • Grasp the end of the wire with the pliers to properly shape the wire.
   • The hook does not need to be perfect, it just needs to be able to hold the foil pieces in place.
7. Cut two triangle shapes out of aluminum foil. The size of the triangles will slightly depend on the size of your jar. You don’t want them to touch any sides of the jar. A good starting point is to make the height of the triangle about {{safesubst:#invoke:convert|convert}} and the base around {{safesubst:#invoke:convert|convert}}. Cut out two separate triangles, but make them identical.
   • Punch a small hole into the top of each triangle. The hole needs to be large enough to fit through the copper wire.
   • If you rip the foil leaf, simply make a new one.
   • Avoid crumpling the foil during this process. Try to leave them as smooth as possible.
8. Hang the triangles on the copper hook and screw the lid onto the jar. Hang each triangle onto the copper hook you made. Make sure the foil leaves are touching each other.
   • If the leaves do not touch each other, try altering the shape of the hook so that they can touch.
   • Carefully, screw the lid onto the jar to complete the electroscope.
9. Test the electroscope with a charged balloon. Rub a balloon on your hair to charge it with static electricity. Bring the balloon close to the copper spiral and watch the foil pieces push each other apart. The electrons transfer down the copper wire and into the foil. Because both pieces of foil become negatively charged, they repel each other.
   • You can also rub the soles of your shoes rapidly on carpet and then place the electroscope near your shoes.
   • Testing works best on a dry day because the electrons cannot escape into the moisture of a humid day.

Making a Pith Ball Electroscope

1. Gather your materials. A pith ball electroscope works on the same principle as the foil leaf electroscope, but looks a little bit different. To make a pith ball electroscope you will need:
   • A small piece of aluminum foil
   • A foam cup
   • An aluminum pie plate
   • A plastic straw
   • Hot glue or tape
   • Thread
   • A balloon
   • A foam plate
   • A ruler
   • Scissors
2. Push a plastic straw through the bottom sides of the foam cup. Make two holes near the bottom of the cup on opposite sides and slide the straw into place. Position the straw so that three to four inches sticks out on one side of the cup.
   • Secure the straw to the cup with tape or a little bit of glue.
   • Avoid making the holes too large or ripping the base of the cup.
   • It’s okay if the base of the cup has a hole in it as long as the straw is stable in its place.
3. Attach the top of the cup to the pie plate. Turn the cup upside down so that the bottom of the cup is facing up. Tape or glue the top of the cup to the pie plate. Position the cup towards the edge of the pie plate so the straw sticks out over the edge.
   • Make sure to secure the cup firmly to the bottom of the plate.
   • Use caution when using hot glue as it is very hot and can cause burns.
4. Crumple a 1-inch square piece of aluminum foil into a ball. Measure and cut out a one-inch square of aluminum foil. Crumple it tightly into a spherical shape. Try to make it as evenly crumpled as possible so that it looks like a foil marble.
   • The square does not need to be exactly 1-inch, it just needs to be a small marble-shaped aluminum ball.
5. Hang the foil ball from the straw with a piece of thread. Cut a piece of thread long enough to hang the foil ball from the straw without it touching the table (about 2-3 inches should be enough). Tie the thread around the foil ball and knot it in place. Tape the other end of the thread to the end of the straw. The foil ball should hang straight down from the end of the straw.
   • Make sure the foil ball hangs close to the edge of the pie pan, but does not touch it.
6. Test the electroscope with a charged foam plate. Rub the foam plate against your hair or a rubber balloon to charge it with static electricity. Place the electroscope on top of the plate and observe what happens. The foil ball should move away from the pie plate. The foam plate transfers electrons to the pie plate and gives it a negative charge, repelling the foil ball away from it.
   • When picking up or moving the electroscope, carry it by the foam cup. If you touch the pie plate, the charges will change and it will not work properly.

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Sources and Citations

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