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09-03-2011, 08:46 PM   #1
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## Multimeter vs Potentiometer

Playing around with electronics, little confused on something.

If two resistors in series, the potentiometer gives .2 miliamps after the first resistor and .1 milliamp after the second. My multimeter just says 3 volts everywhere though.

Does this mean that:
- a potentiometer measures current, which is lowered by resistors.
- a multimeter meter measures voltage, which is constant throughout the circuit

Is this true? Like, if I have a 9volt circuit, and insert a 10k resistor, is it still 9 volts after the resistor?

09-03-2011, 08:52 PM   #2
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A potentiometer does not measure anything. Think of it like the dimmer switch for your dining room lights. As for a multimeter, it is a tool that can be used to measure amps, continuity, Ac or Dc voltage. Next time, do your own homework. Here, this will help you with your questions. http://www.allaboutcircuits.com/vol_1/index.html

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09-03-2011, 08:57 PM   #3
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Quote:
 Originally Posted by tibberous Playing around with electronics, little confused on something. If two resistors in series, the potentiometer gives .2 miliamps after the first resistor and .1 milliamp after the second. My multimeter just says 3 volts everywhere though. If the resistors are in series the current will be the same through all components in the series circuit. To measure current, the meter is also placed in series with the circuit. Does this mean that: - a potentiometer measures current, which is lowered by resistors. A potentiometer is a variable resistor - a multimeter meter measures voltage, which is constant throughout the circuit A multimeter can measure voltage, current, and resistance. Current is constant in a series circuit, voltage drop occurs across components in the circuit. Is this true? Like, if I have a 9volt circuit, and insert a 10k resistor, is it still 9 volts after the resistor?
Yes to your last question. The 10K resistor will drop 9 volts.

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 09-03-2011, 08:59 PM #4 Member   Join Date: Mar 2007 Location: Eighty Four, Pa.15330 Posts: 1,597 Rewards Points: 1,192 Amperes the way you want to read have to be read in series.
 09-03-2011, 09:01 PM #5 Member   Join Date: Mar 2010 Posts: 375 Rewards Points: 264 I'm using the electronics learning lab from radio shack - which refers to the meter as 'meter'. It measures current, so I'm guessing it's called an ammeter? Guess the question I still have is, do resistors change voltage? V = I * R , so it would make sense that changing the current would change the voltage. It doesn't appear to work that way though - the voltage stays 3, regardless of resistor, according to my multimeter.
 09-03-2011, 09:03 PM #6 Member   Join Date: Dec 2006 Posts: 17,158 Rewards Points: 6,652 http://www.csgnetwork.com/ohmslaw2.html Here is the U.S. Army basic fundamentals of AC & DC. http://www.scribd.com/doc/3006265/TC...iples-of-AC-DC It is a lot better resource, than that Ratshack material that is pretty much out dated, and some parts of that book's printed material is actually incorrect in a few spots. Last edited by gregzoll; 09-03-2011 at 09:07 PM.
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09-03-2011, 09:07 PM   #7
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Quote:
 Originally Posted by tibberous I'm using the electronics learning lab from radio shack - which refers to the meter as 'meter'. It measures current, so I'm guessing it's called an ammeter? Guess the question I still have is, do resistors change voltage? V = I * R , so it would make sense that changing the current would change the voltage. It doesn't appear to work that way though - the voltage stays 3, regardless of resistor, according to my multimeter.
Is the power for this learning lab provided by two 1.5 volt batteries?
A meter that strictly measures current is an ammeter.

09-03-2011, 09:16 PM   #8
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Quote:
 Originally Posted by a7ecorsair Is the power for this learning lab provided by two 1.5 volt batteries? A meter that strictly measures current is an ammeter.
No, it takes 6. It has breadboard with different voltages across the top rail.

I figured out what was going on too. The voltage never reads exact, it's just close to what it should be. When I added my resistor, it did drop, just not enough to notice. I added a much higher resistor and was able to see the voltage drop.

 09-03-2011, 09:23 PM #9 I=E/R     Join Date: May 2010 Location: Minnesota Posts: 2,052 Rewards Points: 1,000 In this circuit no matter what size resistor is installed, the voltage on the meter will be 3 volts but the amount of current flowing will change according to ohms law. Attached Thumbnails
09-03-2011, 09:26 PM   #10
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In this circuit the current will remain constant. The voltage measured on the wiper of the potentiometer will change as the knob is turned.
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