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## Homework Statement

A voltmeter whose resistance is 1000 ohms measures the voltage of a worn out 1.5V battery as .9V. What is the internal Resistance

## Homework Equations

## The Attempt at a Solution

In order to do this, I Solved for the Equiv Resistance of the circuit (leaving in the unknown Ri) by assuming they were two resistors in parallel. as:

Requiv=(1000+Ri)/(1000Ri)

Using ohms law I calculated the current through the circuit:

1.5=IRequiv

Plugging in my answer for Ri and simplifying I got:

I=(1500+1.5Ri)/1000Ri

Now assuming the resistors are in parallel, I would know that the current through each resistor is the same, meaning that I would get:

V=IRi

assuming the voltage drop across Ri as .6V (because 1.5-.9 is .6) I plugged that in and got:

.6=(1500+1.5Ri)/1000

However, when I solved for Ri, I got a negative number!

Help would be great!!

Next, thinking that they were in parallel, the current through both resistors was the same, so