Can a Human Circuit Light an LED bulb?

This past year when we were building lemon batteries, students had many of their own investigative questions.  For one, students wondered if lemon juice would light an LED bulb.  As a result, we tested lemon juice, apple juice, salt water, and many other liquids.  Acting on their own questions fueled even more curiosity.

One student wondered if we could build a human circuit.  I didn’t think it would be possible to light an LED bulb with a human circuit.  I researched it on Google before I tried this activity with the students, and I found NOTHING about being able to light an LED with a human circuit.  I had the students predict whether they thought that we could accomplish the lighting of an LED.  Only about three out of ten students thought we could light the bulb.

Here is what we did:

1. I had each student get one alligator clip wire to connect a pre-1982 penny and a zinc nail.  (Doing this will give you about two more wires than you need, but at least everyone is busy.)
2. I had about 10 students stand in a circle.
3. Then each student in the circle held one pre-1982 penny in one hand between two fingers and with the other hand held one zinc nail between two fingers.
4. Between each of the sets of students in the circle, I had the students hold the wire of an LED bulb.  One student held one wire (positive) coming out of the bulb while another student held the other wire (negative).
5. I made sure everyone was making a complete circuit for the electricity to pass through.

Then I heard the unthinkable.  “I saw it light up!”  one child exclaimed.

Now, I thought the students just saw a reflection, and it really wasn’t lighting up. Speaking to myself here—“Oh, ye of little faith.”  Children are so optimistic, and I was blatantly reminded of my pessimism at this moment.

I turned off the lights because I wanted to be sure they weren’t imagining this. Sure enough, the electrical current flowed through all of the kids to create a human battery and light up an LED!!!

Side note:  In case you aren’t having success with your human circuit.  Make sure each child is actually making connection with a penny and a nail.  There must be a penny, nail pattern in the circle.  Flip the LED bulb the opposite direction if it doesn’t work the first time since each of the wires/prongs coming out of the LED are either positive or negative.

This could be an amazing team building experience with your students at the beginning of the year!