*84.  Determine the voltage across the 5.0 Ω resistor in the drawing. Which end of the resistor is at the higher potential?

 

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Figure below provides currents and reference points for writing out a set of Kirckhoff laws.

Do a junction rule at point B

 

Need two loop rules, do one on left start on point A and go clockwise, for the second do right loop start at point B and again go clockwise.

 

 

 

Need to solve for i1 in order to find voltage across the 5.0 resistor.  So the simplified set of equations presented below.

 

 

 

 

Use the relationship from the junction rule to substitute for i2 in the two loop equations

 

 

Simplifying these two expressions

 

 

 

Multiply the first equation by 2 and then subtract the second equation from the first.

 

 

 

So the voltage across the 5.0 Ω is

 

Since the current found is positive, the assumed direction of i1 is correct.  Therefore the voltage would drop going to the right, which means the left side of the resistor is the higher voltage.

 

 

 

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This page last updated on June 18, 2018