Electric Science: Make a Battery!

What You Need:

  • ⅓ cup lemon juice
  • 9 pieces of paper towel, each 1”x 1” in size
  • 5 shiny, clean pennies, 5 zinc-coated washers, about ¾ inches in diameter (available at hardware stores)

What You Do:

  1. Explain to your fourth grader that she will be doing an experiment to find out what happens inside a battery to make it work, and she’ll do it by combining pennies, zinc washers, and lemon juice. Sound weird? She’ll just need follow directions closely, and be ready to explore some new things while she’s at it!
  2. If you haven’t done so already, cut the paper towels into 1” x 1” pieces, and soak your nine pieces thoroughly in the lemon juice, so that no part of the towel is dry.
  3. Put one washer on a clean surface. Have your child place a paper towel square over it, and then place a penny over that. Help her to alternate this way, with a paper towel piece between each coin or washer, until you have used all ten pieces.
  4. Now make sure your child’s thumb and middle finger are wet, either with lemon juice or water. Have your child pick up the stack using thumb and middle finger, making sure that the finger is touching metal, not paper towel.
  5. She has just made a battery and her fingers are what completed the circuit! You can measure the mild electric charge by using a voltmeter (a battery tester), and putting each prong on one side of the stack. Or take a page from the Volta's notes: according to his findings, your child should feel a tingle in her fingers when she holds that stack!

What’s Happening?

You’ve just replicated the basic workings of a battery, which actually consists of two different metals surrounded by strong acid. One of the metals has a negative charge, and one has a positive one. When your child used moistened fingers to pick up the coin stack (with a washer on one end and a penny on the other), she completed a “circuit,”—a mild version of what happens when a battery powers a flashlight, or radio, or computer game!

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