What do lightning, a toaster oven, and static shock have in common? Electricity, of course! It’s what runs the conveniences that fuel our modern lives and makes our hair stand on end. It powers the screen that lets you read this article!

But you might not have known just how pervasive electricity really is in our universe. In fact, electricity is present at all times in the atoms that comprise living beings. At the center of an atom is a nucleus of positively charged protons and neutrally charged neutrons, and then surrounding the nucleus in a constantly moving cloud are negatively charged electrons.

For an atom to have a net neutral charge, the number of protons must equal the number of electrons. Atoms aren’t sentient beings with preferences like you or I would have, but we can think of them as “liking” to be in a neutral state. Sometimes, though, the atom has more or less electrons than its number of protons. In that case, it has a net charge and we call it an ion. Positively charged ions (less electrons than protons) are called cations and negatively charged ions (more electrons than protons) are called anions. You can remember which is which because the “t” in the middle of “cation” looks like a plus sign, and the word “anion” can be broken down into “a n(egative) ion.” Cool, right?

Because atoms “like” to be neutral, a cation is going to want to gain electrons to offset that extra positive charge, and likewise, an anion is going to want to lose electrons to get rid of its negative charge. This means that to restore the balance of charges, electrons have to get transferred from one atom to another.   

As Rachel said in this week’s segment of Cool Science, “Electricity is the movement of electrons from one atom to another atom.”

It’s that simple! The movement of electrons even has a special name that I’m sure you’ve heard before: a current. When materials are composed of atoms that are really good at letting this electron transfer happen, we say that they are conducive to electrical current. They are conductors. On the other hand, if a material is not super good at conducting a current, we call it an insulator.  

In this experiment, you’ll get to see for yourself what kinds of things are conductors and what are insulators. The results might surprise you! If you’re curious as to why each material is or is not a conductor, check out the explanation section below the instructions (but don’t peek yet if you’re planning on doing the experiment yourself– it’s so much more fun to make your own discoveries first than to skip ahead to the spoilers!).

You’ll need:

  • 1 raw potato
  • 1 orange
  • 1 whoopee cushion
  • Electrodes: 1 copper, 1 zinc
  • 1 small, low voltage clock (you can also use a small light bulb)
  • A human friend


  1. Remove the batteries from the clock and plug your electrodes into the positive and negative terminals where the battery normally sits.
  2. Stick the ends of the electrodes into the potato. Does the clock turn on?
  3. Place the ends of the electrodes on the sides of the whoopee cushion. Does the clock turn on?
  4. Stick the ends of the electrodes into the orange. Does the clock turn on?
  5. Hold the ends of the electrodes in your hands. Does the clock turn on? Get your friend to add his or her hands to the electrodes so that you’re both touching them. Is the clock any brighter?


  • Potato: conductor! The sap inside the potato causes an electrochemical reaction in place of the chemicals inside a typical battery. You’ve just made a vegetable battery!
  • Whoopee cushion: insulator! Rubber is not a material conducive to electrical current.
  • Orange: conductor! Rather than sap, as we saw with the potato, it’s the acid in the orange that allows it to be a conductor. You’ve just made a fruit battery!
  • Human being: conductor! That’s right, people can conduct electrical current because the thin film of sweat on the skin acts like the potato sap or orange juice– as a substitute for battery acid! And the more people add their hands to the electrodes, the brighter the clock gets.