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I have a simple breadboard setup with my multimeter inserted to measure the current. I'm trying to see current changes from different resistors. No matter what resistor I seem to put, the current doesn't change. NonWorkingTransistors Is this because nothing is drawing charge? (does this have anything to do with the law conservation of charge?)

I'm trying to get the current right on my circuit before I hook it up to a little motor. I can't hook up my motor until I get the current right so I have nothing to hook up to my circuit to draw current. Is there a way I can cause a circuit to draw current so I can correctly read reduced voltages? Or could something else be wrong?

(I was using a rechargeable lithium ion 9volt and then switched to a regular one to see if that was it. But a lithium ion power source shouldn't effect current right?)

enter image description here

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  • \$\begingroup\$ can you draw a circuit diagram and post it here? Its hard to see where each wire is going in your picture. Maybe take a top view pic? Also your Multimeters red wire is floating (if i am seeing this correctly). \$\endgroup\$ – stackErr Nov 15 '13 at 1:28
  • \$\begingroup\$ Is that better? \$\endgroup\$ – stormist Nov 15 '13 at 1:39
  • \$\begingroup\$ Post a picture of your meter, so that we can see how it is setup and your actual measurement. \$\endgroup\$ – apalopohapa Nov 15 '13 at 1:52
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    \$\begingroup\$ Can you post the reading of your ammeter and the resistor you are using? As well as how much current/voltage your motor needs? \$\endgroup\$ – stackErr Nov 15 '13 at 2:19
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I can't tell you what the problem is with your apparatus since the photos can only give a limited amount of information.

However, it appears from the photo that you just have a voltage source (battery) in series with a resistor in series with an ammeter (you do have the multimeter set up to measure current and the leads connected to the proper inputs, correct?).

Now, this is certainly a valid connection and, if the above is a correct description, you should be able to measure different current values for different resistor values (however, if your multimeter and leads are set to measure voltage instead, you will only measure the battery voltage regardless of the resistor value).

However, with such a simple circuit, you can simply use Ohm's law to calculate the current.

Since an ammeter is effectively a short circuit, the current through the resistor is simply the battery voltage divided by the resistance.

In other words, if you simply connect the resistor directly across the battery and then measure the voltage across the parallel combination, the current is simply the measured voltage divided by the measured resistance.

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  • \$\begingroup\$ Thank you so much for being so polite on my noobie question. It was wrong setting on multimeter. \$\endgroup\$ – stormist Nov 15 '13 at 3:35

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