- #1
Potatochip911
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Homework Statement
A real battery can be modeled as an ideal voltage source in series with a resistor. A voltmeter with input resistance of ##1000\Omega## measures the voltage of a 1.5V worn out battery as 0.9V. What is the internal resistance of the battery.
Homework Equations
##V=IR##
The Attempt at a Solution
After I had already drawn the circuit I realized it's wrong to have a wire with nothing on it along the right side but it's painful to draw the circuits so I'll just mention to ignore that section rather than redraw it.
I'm quite lost as to how to solve this question, the battery has a voltage of 1.5V so ##V_0=1.5V## but the voltmeter is reading 0.9V. Now without the right hand portion of the circuit ##R_v## and ##R_i## are in series so the current is given by ##i=\frac{v_0}{R_v+R_i}##, now from KVL ##v_0=i(R_v+R_i)## but my ##i## will just cancel out everything and I'll end up with essentially nothing. Not really sure what to do with the voltmeter reading 0.9V.