123V. at the power supply, at the end of the run i'm getting 90V. what is the resist
- Thread starter zappy
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jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
Length, load, and wire size?
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
current will give you the impedance of the run, and with the impedance known, knowing the length will give you the wire size, or knowing the wire size will give you the length all can be figured from the 33 volt drop if the load didn't change from the time you took one measurement till you took the other, basic ohm's law.
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kwired
Electron manager
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- NE Nebraska
You need to know what the current is and then you can use Ohm's law to calculate the resistance.
Make sure the load is operating to when taking voltage measurement at the source. If the source is too small or has an excessive small length it too will drop with load on it.
K8MHZ
Senior Member
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- Electrician
You need to know at least one more thing. Current would be easiest.
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- Chapel Hill, NC
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- Retired Electrical Contractor
Think of ohm's law. There are 3 variables. You really can't solve an equation with one known variable. You need two knowns to solve a 3 variable equation.
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