Small Resistor Value - Question

[Stocky]

Hi everyone,

I have a question about the voltage drop across a resistor with a small resistance i.e. <10 Ohms.

My simple circuit to test this is a voltage source in series with a resistor. The resistor has a value of 4 ohms and is rated at 1W.

If I set the voltage source to 1V I expect a 1V drop across the resistor. However with the 4 Ohm resistor the voltage drop is only 0.6V. If I use a 100 Ohm resistor instead it works as it should, a 1V drop.

Can anyone please explain to me why this is happening?

Thanks,
Chris

 

[davenn]

Hi there
welcome to EP

it may be measuring error with your meter

what is the voltage source ?


The other very significant possibility and the most likely cause, is that the 4Ω
is loading down the PSU and causing a voltage drop on its output

so with that in mind, were you using current limiting? if so, to what limit?


Dave