Science Buddies: "Ask an Expert"

Hello!

My kids have chosen the 'Battery that makes Cents" project for their Science Fair at school. Throughout the experiment the voltage increased when increasing the number of coins. But the current always read as '0'. We did the experiment until there were a total of 8 coins. But everytime the current measurement was '0'. We made sure the paper towel pieces do not touch each other. Any advice would be greatful.

Thank you!


[Administrator note: Project link: https://www.sciencebuddies.org/science- ... #procedure ]

damithrif - If you are getting appropriate voltage readings in each cell, it is likely that the method to measure current is the problem. Make sure your meter settings are correct. You have to be set to DC current using a very low range, perhaps 20 milliamps to begin with. Also verify the probes are plugged into the proper sockets. Typically the black lead is in the COM socket and the red probe into the Volt-Ohm-Amperes or similar. If you have access to a resistor, any value between 100-10,000 ohms, simply place a small battery, AA or AAA is fine, in series with the resistor and see if you can measure any DC current to see if your meter is functioning in the current range. If that doesn't work there might be a problem with the meter, possibly a fuse issue. If you need additional help, let us know more about the meter you are using.

Rick Marz

Hello. We were experiencing the same issue last night of being able to read voltage but not mA. We discovered through a friend that on our multimeter in order to read mA we had to remove the red cord and plug it into the white mA fuse hole. Hope this helps.

@rickmarz - Thank you for your reply. We tried all that. Still the same result. So I guess the multimeter must be defective.

@runnels09 - Maybe it's the same for our multimeter. We will try this. Thank you.