# Measuring voltage drop across 10 ohm, 100 ohm and 10 kilohm resistors (one at a time) - very simple circuit

Below is a picture of my very simple circuit.

There are three resistors 10 ohm, 100 ohm, and 10 kilohm. I connect them one at a time in serial fashion and measure voltage drop across them. When I measure battery voltage I get 6.5 Volt and this is what I expect as voltage drop on all of my measurements, but here is what I get:

1. When I measure voltage drop across 10 ohm resistor I get 0.2 volt.
2. When I measure voltage drop across 100 ohm resistor I get 1.0 volt.
3. When I measure voltage drop across 10 kilohm resistor I get 5.8 volt.

Why do I get all these different readings and not something around 6.5 Volt?

P.S. On the image the circuit is not closed, but this is how I took picture, circuit is closed on all measurements.

• this question has been asked here a lot ... the rest of the voltage is dropped across the battery internal resistance ... |l------\/\/\-----\/\/\----- Apr 2, 2021 at 21:50
• Pay attention not to fry the 10 Ohm resistor when using a fresh battery. Apr 3, 2021 at 5:44
• @tobalt, I already saw it smoking ;-). How do I decide what current resistor can withstand? Apr 3, 2021 at 13:34
• In this simple circuit, the worst case power in the resistor will be 81/R Watts. The resistor are probably rated for 0.25 W... The real power will be less because of internal Resistance in the battery but don't go grossly over this limit. Apr 3, 2021 at 14:17

A fresh Panasonic alkaline battery (consumer grade, not industrial) has an internal resistance of less than 4$$\\Omega\$$.