Electrical – Find voltage across Resistor w/ Op Amp

operational-amplifierresistors

I was wondering if you guys could help me or lead in the right direction. I need to find the voltage across a resistor with an op amp. I was originally going to try solving for nodal voltage. But we can't do that. And usually we can do the Rf/Rs*Vin but it is throwing me off cause there is no Rf so it would be 0?

What is the voltage before and after the op amp?

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Best Answer

Since you are using an op amp as a non-inverting amplifier, your gain equation is wrong. Rf/Rin applies for an inverting amp, and you have left off the - sign in your relation. The general configuration for a non-inverting amplifier is

schematic

simulate this circuit – Schematic created using CircuitLab

So for your configuration (called a voltage follower) the gain is 1 plus (zero /infinty) or 1.