# Why doesn't my wire follow ohm's law?

I have a 60mm length of wire with diameter of 0.5mm. Meaning it should have a resistance of 0.005 ohm.

I put a constant voltage of 0.3volt through it, but it's only taking 7amp, but according to ohm's law, shouldn't it be able to take 58.5amp?

My power supply has a max output of 10amp, so shouldn't it take at least 10amp? Because I know for a fact the power supply can put out more, because if I turn up the constant voltage to 0.5volt, it will take 10amp.

You have two problems.

First, the obvious, you have not taken the resistance of probes into account. Ohm's Law must be satisfied.

Second, TP-60052 TWINTEX is a Dual Channel Power Supply only rated for 5A, 10A if you place channels in parallel. Impressive getting 7A from a 5A power supply. But it cannot supply your loads needs. This is probably why your voltage is 0.3V. Voltage and Current settings appear to be at MAX. The Power Supply is trying, but you have effectively put a short circuit across output.

The capabilities of the test gear combined with test lead resistance means you will never get 58.5A, no matter what you do.

Did you include the resistance of the red and black wires?

Also measure the voltage dropped acros the resistor directly and also take into account the resistance of the meter.

Extend SolarMike answer, I suggest you directly measure voltage at the leg of your wire. Since you know the current 7 Ampere, and voltage reading between two legs of your coil wire - you can know the wire resistance (should be close to 0.005 ohm).

Let us know the result, and we can extend the discussion/test bench further (for better understanding).

NB: measure the voltage using separate voltmeter, since your 0.3V is not voltage between legs of your wire. Voltage drop between your wire will be below 0.3V .

I agree with SolarMike that you need to measure the resistance of the entire system (wires+ resistance).

Additionally, my suggestion is to that you take a few measurements at different voltages and plot the IV curve (e.g. 0.1, 0.2). That might be more illuminating for debugging.