Show that the voltage across resistor R2

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    Resistor Voltage
AI Thread Summary
The discussion focuses on deriving the voltage across resistor R2 in a circuit using conservation of power. It emphasizes that the same current flows through all components, leading to the equation for power supplied equaling power absorbed. The correct relationship for voltage across R2 is derived as v_{R_{2}} = v_{s} * (R_{2} / (R_{1} + R_{2})). Participants express confusion about applying Ohm's law and the power equations correctly. The key takeaway is that the problem highlights the absence of internal resistance in the voltage source, simplifying the analysis.
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Homework Statement



In the circuit shown, the same current must flow through all three componets as a result of conservation laws. Using the fact that the total power supplied equal the total power absorbed, show that the voltage across resistor R2 is given by:

v_{R_{2}} = v_{s}\frac{R_{2}}{R_{1} + R_{2}}

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Homework Equations



p = vi = i^{2}R = \frac{v^{2}}{R}

The Attempt at a Solution



I said:

p_{v_{s}} = p_{R_{1}} + p_{R_{2}}

because power supplied = power absorbed

p_{v_{s}} = p_{R_{1}} + p_{R_{2}}

But I don't think this is right because it would not simplify right.

v_{s}i = i^{2}R_{1} + \frac{v_{R_{2}}^{2}}{R_{2}}
 
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Since total power supplied is equal to the total power absorbed, there is no internal resistance in Vs.
Apply the ohm's law to the circuit and find VR2.
 


I am still having trouble with this.

I know Ohm's law is

v = IR

I = \frac{v}{R}

and

R = \frac{v}{I}

but do I just just use them with this:

p_{v_{s}} = p_{R_{1}} + p_{R_{2}}

v_{s}i = i^{2}R_{1} + \frac{v_{R_{2}}^{2}}{R_{2}}
 


What is the total resistance in the circuit?
What is the current in the circuit?
And then what is the voltage across R2?
Here you need not use the power formula.
In the problem the mention of the power is to emphasis the absence of internal resistance in the source.
 
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