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Homework Statement
Given this following circuit:
What is the internal resistance of the meter movement ( R_I).
This is part of a project I'm doing and I know the equation that gives you the internal resistance in this circuit.
$$R_I = \frac{R_sR_p}{R_s  R_p}$$.
However, I have no idea how this is derived. I know the values for V, R_s and R_p as it was done experimentally.
Homework Equations
$$R_I = \frac{R_sR_p}{R_s  R_p}$$.
$$ V = IR $$
The Attempt at a Solution
Using circuit analysis I can simplify the parallel portion as:
$$ R_{parallel} = \frac{1}{R_p} + \frac{1}{R_I}$$
Thus:
$$R_{total} = R_s + \frac{1}{R_p} + \frac{1}{R_I} $$
But what is R_total, how do I get rid of it?
Thank you for any guidance.
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