Science Buddies: "Ask an Expert"

Hello!

We are trying to make a voltaic pile that turns on either a small LED light or a motor. We are using zinc-plated washers, cardboard soaked in a vinegar/salt solution, and pennies. The LED light we have requires around 1.5v, but the motor is supposed to work as long as it has anywhere between 2v and 4v. We also have a multimeter so we can see what voltage it is producing.

We have found that we need between 7 and 10 cells (cell = penny, cardboard, washer) to reach the desired voltage. However, when we touch the motor or LED wires to the ends of the pile, nothing happens. We also check the motor/LED with a 3v disk battery, and they turn on. So it's not the motor or LED. The multimeter says we're in the same range of voltage for the manufactured battery and the pile.

What is going on? Does it have something to do with current or amplitude? What could we be overlooking? There are plenty of videos on YouTube that show this to be a successful experiment, yet we just cannot get it to work! Is this usually a temperamental experiment? Or, if you don't know the answer, what have you all found to be common issues with this experiment? What tips or tricks did you find?

Thank you for any help!!

-Amy

Hi Amy - for any given electronic device, you need enough voltage AND current to power it. LEDs typically require about 2 volts and around 20 milliamps (mA). Small motors may require a similar voltage, but usually require much more current (hundreds of milliamps). The 3V battery you are using has a similar voltage to your voltaic pile, but can probably provide much more current, which is why it can make the LED and motor turn on.

If you are following the Science Buddies version of this project, it has instructions for how to measure the current produced by your cell - that should let you know if your current is at least in the right ballpark:

https://www.sciencebuddies.org/science- ... #procedure

We have a pretty extensive resource on multimeters if you need more information there: https://www.sciencebuddies.org/science- ... multimeter

Our FAQ also covers some common issues you may encounter when trying this project:

https://www.sciencebuddies.org/science- ... coins#help

Hope that helps!

Ben