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I am trying to make an electromagnet so I bought magnet wire to wrap around an iron core. I am pretty sure that there is a current running through the copper wire because I attached an alligator clip to one end of the wire and in the process and created a gap and saw sparks. I also tried burning with a lighter the insulator and scraping that part off. I attached the ends of my multimeter to check current and it is showing a very small voltage, like ~100 mV, though my power supply is 9V. I checked to see if my electromagnet is magnetic and just weak and it is not working. I tried using a potentiometer to put current instead of voltage and I got nothing. I am really confused and could use some help.

Thanks in advance!

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    \$\begingroup\$ it is showing a very small voltage, like ~100 mV, though my power supply is 9V smells like the power supply goes into short-circuit protection. Try to measure the winding resistance with your DMM. \$\endgroup\$
    – Rohat Kılıç
    Commented Jun 25, 2020 at 5:40
  • \$\begingroup\$ You may well have damaged your potentiometer by essentially shorting a 9V battery through it, if it was turned almost all the way down in resistance. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jun 25, 2020 at 11:19
  • \$\begingroup\$ It seemed to function the same. What are the signs of a damaged potentiometer? \$\endgroup\$
    – Vivek Ramadhar
    Commented Jun 25, 2020 at 17:18
  • \$\begingroup\$ You might not know that most magnet wire does not have that insulation that can be burned away with a flame. That is a particular type of insulation, not the usual. To remove the insulation, use mechanical means or some chemical means. \$\endgroup\$
    – user69795
    Commented Jul 6 at 16:13

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The traditional 19th century method is to get a compass. Away from your apparatus, it will point to magnetic north. Any magnetic field will deflect the needle.

But your iron core may already be slightly magnetized. A compass should be sensitive enough to detect a current in a wire, even without (or away from) the iron core.

If your 9V supply is only putting out 100mV, then the chances are you have successfully short circuited it by connecting a bit of copper wire straight across the terminals. Electromagnets either need a high current at low voltage, or lots of turns of wire to increase the resistance.

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  • \$\begingroup\$ I'm sorry if this an extra dumb question, this is my first dive into electronics, but how would I know for certain if my battery is shorted? I checked voltage values for the two I had at my desk (i forgot which one I was using) and one measured 8.79v and the other 9.57v . Based on another stack exchange thread it seems like the 8.79 one discharged due to the short circuit but I just want to confirm. \$\endgroup\$
    – Vivek Ramadhar
    Commented Jun 25, 2020 at 8:00
  • \$\begingroup\$ You know it's shorted when the voltage collapses to (almost) 0V. An electromagnet is essentially only a bit of copper wire coiled up. Unless it's a very long thin bit of copper wire, its resistance will be very low. \$\endgroup\$
    – Simon B
    Commented Jun 25, 2020 at 11:05
  • \$\begingroup\$ @VivekRamadhar An electromagnet basically is a short circuit, it's just a useful one. That's why electromagnets are made from long and thin wires - to make a very "long" short circuit. If that makes sense. \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Jun 25, 2020 at 14:08
  • \$\begingroup\$ Yeah, that sort of makes sense. Thanks for the help! \$\endgroup\$
    – Vivek Ramadhar
    Commented Jun 25, 2020 at 17:16

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