Science Buddies: "Ask an Expert"

Hello. We are doing a science project to test the strength of an electomagent. When we switch from a 6V lantern batter to a 9V regular battery, the electromagent does not work anymore. We think this has to do with the size of the battery since the 6V is much larger, but the 9V has more voltage. Can anyone explain how this works?

Hello!

What a fun project. When you switched from a 6V lantern battery to a 9V regular battery and the electromagnet stopped working, it likely had to do with the type of battery, not just the voltage. While the 9V battery has more voltage, it’s much smaller and can’t provide as much current as the larger 6V lantern battery. Electromagnets rely on strong current to work well, and the lantern battery is designed to deliver that. The 9V battery, on the other hand, is built for low-power devices and can’t handle the current your electromagnet needs, so it ends up not working. In short, the bigger battery is better here because it can supply more power, even at a lower voltage.

Hello and thank you! Yes, this makes sense. We may try measuring the current then to help explain what happened. We assumed the current would be constant.

Hi - chiming in to say that you need to be careful when measuring the current through an electromagnet, because you can easily blow the fuse in your multimeter. I'd recommend watching our "how to use a multimeter" tutorial video if you haven't already: https://www.sciencebuddies.org/science- ... multimeter, and when you measure current, make sure you start out with the high-current port and dial setting (for example, 5A or 10A) on your meter to avoid blowing the fuse.

If you want to learn more about voltage, current, and their relationship, I recommend doing some research about the topics of "Ohm's Law" and "battery internal resistance," which will explain more about what's going on with the 9V and 6V batteries here.

Very cool and thank you for the advice! We'll save this bit for last, then, and do it safely!