# voltage drop measurements

#### beargo

Joined Nov 26, 2005
2
hello, i am new to electronics. i am using a basic electronics book to do simple projects that show how to measure different values of components. i am having a problem getting accurate readings . when i try to get a voltage drop from a resistor inserted in a circuit i dont see any diiference from the full dc source voltage. it doesnt matter what size resistor i put in the circuit i dont get any voltage drops. i do get accurate current drops . i have tried measuring in paralell and series. also i have used two different meters. any suggestions or help would be apprieciated. thanks.........dave w.

#### beenthere

Joined Apr 20, 2004
15,819
Hi,

When your circuit is really simple, like one resistor and one voltage source, then all the voltage appears across the risistor. You have to add another resistor in series with the other in order to be able to see a voltage drop.

#### Murod

Joined Dec 24, 2005
30
Every non-ideal voltage source has an internal resistance, so it will suffer voltage drop when You connect a load to it. The amount of the voltage drop depends on the internal resistance and the resistance of the load. You don't see the voltage drop because the internal resistance is much lower than the load you connect. Imagine that you connect a 1k Ω , then you measure the voltage drop. Then You try 100 Ω ,10 Ω , 1 Ω , 0.1 Ω , 0.01 Ω (or You short it). Will You still get a full dc voltage? I don't think so.