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Measuring voltage drop
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jarrett_1
- Posts: 1
- Joined: Sun Feb 22, 2015 3:23 pm
- Occupation: student
- Project Question: Measuring voltage drop across different gauges of wire, using a millimeter to measure.
- Project Due Date: May 1, 2015
- Project Status: I am conducting my research
Measuring voltage drop
I was planning to use a multimeter to measure the voltage or voltage drop of 5 foot pieces of copper wire of varying gauges. Using a 9 volt battery, I attached the wire to the battery and the leads from the multimeter to other ends of copper wire and battery. The meter read 9 volts when attached to the copper wire and 9 volts when measure just using the leads. There was no change. Is there some other measurement I should be making or do I need to redo my hypotheses and variables. If so, what should it be? Help.
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deleted-249560
- Posts: 496
- Joined: Thu Nov 20, 2014 1:35 pm
- Occupation: Science Buddies content developer
- Project Question: N/A
- Project Due Date: N/A
- Project Status: Not applicable
Re: Measuring voltage drop
Voltage drop can be little tricky to measure. What you did was simply to extend one of the meter leads with your wire. You're not drawing any significant current so you won't see any voltage drop. The drop will be more apparent as you draw more current.
Take a look at http://www.calculator.net/voltage-drop-calculator.html
If, for example, you attached a light bulb (incandescent, not LED) to the battery through your wire and measured the voltage across the wire, you might see an effect. http://www.digikey.com/product-detail/e ... ND/1553124 is a 10V bulb that you could light with a 9V battery. If you put it right across the battery, it might draw 14 mA or 0.014A. If you disconnect the wire going to positive battery lead and replaced that with 5 feet of 18 AWG wire (a c ommon size used for speakers), the drop across the wire might be 0.00089 V. That's going to to be hard to measure unless you have a really high quality meter. To really see the effect of voltage drop, you may need a much bigger battery and a significant current draw. Perhaps using an automotive lamp like a turn signal bulb and a car battery. In 5 foot sections of wire that might start showing 30 to 50 mV of drop which is something a good 4 1/2 digit meter can read. You might also consider using an entire spool of wire and not just 5 foot section. Unroll it because you don't want to make an electromagnet - 50 feet would definitely show a measurable effect with 12V and a lamp.
Howard
Take a look at http://www.calculator.net/voltage-drop-calculator.html
If, for example, you attached a light bulb (incandescent, not LED) to the battery through your wire and measured the voltage across the wire, you might see an effect. http://www.digikey.com/product-detail/e ... ND/1553124 is a 10V bulb that you could light with a 9V battery. If you put it right across the battery, it might draw 14 mA or 0.014A. If you disconnect the wire going to positive battery lead and replaced that with 5 feet of 18 AWG wire (a c ommon size used for speakers), the drop across the wire might be 0.00089 V. That's going to to be hard to measure unless you have a really high quality meter. To really see the effect of voltage drop, you may need a much bigger battery and a significant current draw. Perhaps using an automotive lamp like a turn signal bulb and a car battery. In 5 foot sections of wire that might start showing 30 to 50 mV of drop which is something a good 4 1/2 digit meter can read. You might also consider using an entire spool of wire and not just 5 foot section. Unroll it because you don't want to make an electromagnet - 50 feet would definitely show a measurable effect with 12V and a lamp.
Howard