Ohms Law Confusion in Arduino

Hi there guys, I’m attaching the image with the series circuit diagram. Basically the Voltage(T) = 4.96 V. And I only have one 219 Ohm Resistor in the series circuit. So by Ohm’s law shouldn’t the volt of the Resistor should be 4.96 V as well? Since V(T) = V0+V1+V2… ? Please help. Because when i measure the volt of the resistor across I keep getting 4.90 to 4.91 V. I need to know where this voltage is going.

Thanks so much.

Well the wires aren't perfect conductors, so there's a little resistance in the rest of the circuit apart from the resistor. That'll be where your 0.05V go, I guess.

The wire used to make the circuit has resistance also so if you are concerned about millivolt accuracy you need to account for it. Ohm's law is not a fault, just a failure to account for all the resistant elements in the circuit.


Only .05V ??

That's nothing, it will be in the wires and connectors.

How do you know that the input voltage is 4.96 V?

If you are measuring that voltage before connecting the resistor, then again after connecting the resistor, then most of the voltage drop will be in the power supply itself.

Your voltage source was not a ideal voltage source, it have internal resistance too, it drop some voltage.