# Is a load needed to measure the voltage drop of a long cable?

Should be a simple yes or no question.

If I attach 20ft of 16AWG cable to a power supply, in theory I should see some voltage drop. Do I need to place a load at the end of the cable to read the actual drop or can I just connect my multimeter to read the end and take that as the voltage available.

• The voltage drop is proportional to the current through the cable. Remember the cable goes there and back if you use Ohm's law to calculate the voltage drop. – Andrew Morton Nov 29 '16 at 16:32
• Without load, you could use a multimeter in "ohm" mode to get the resistance of your cable and deduce the drop from that. Otherwise, if you can only measure voltage, yes you would need a load (with no load, there will be no voltage drop). Now, just to check: are you well aware, however, that the voltage drop will depend on the current through the cable (and therefore on the load)? – dim Nov 29 '16 at 16:32
• y e s . . . . . – Sunnyskyguy EE75 Nov 29 '16 at 16:50
• If you know the gauge and length you can actually calculate it and get pretty good results, so no need to plug different loads on it everytime you want to study a different scenario. – Wesley Lee Nov 29 '16 at 17:01