Current and Voltage values using Ohm's Law

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SUMMARY

The discussion focuses on calculating current and voltage values in a circuit using Ohm's Law and the Parallel Resistance Formula. Given a voltage source (Vg) of 55 V and resistances R1 (3 Ohm), R2 (12 Ohm), and R3 (90 Ohm), the user initially calculated the total resistance as 10.62 Ohm and derived an initial current (I1) of 5.18 A. However, the user encountered difficulties in determining the correct values for I2 and subsequently sought assistance, revealing a miscalculation in the placement of R1 in the resistance formula.

PREREQUISITES
  • Understanding of Ohm's Law (I = V/R)
  • Familiarity with the Parallel Resistance Formula (R_total = R1 + (R2*R3)/(R2+R3))
  • Basic circuit analysis skills
  • Ability to perform calculations involving voltage, current, and resistance
NEXT STEPS
  • Review the application of Ohm's Law in circuit analysis
  • Study the derivation and application of the Parallel Resistance Formula
  • Practice solving circuit problems involving multiple resistors in parallel
  • Explore power calculations in electrical circuits, specifically for resistors
USEFUL FOR

Students studying electrical engineering, circuit designers, and anyone looking to enhance their understanding of circuit analysis using Ohm's Law and resistance calculations.

Kas0988
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Homework Statement


Kirchoff2-3.jpg

In the circuit above given that Vg is 55 V, R1 is 3 Ohm, R2 is 12 Ohm and R3 is 90 Ohm. Using the polarity shown in figure answer the following questions.

(A) Find the value of i3?
(B) What is the value of i2?
(C) What is the value of V3?
(D) Calculate the power dissipated in R1?
(E) Calculate the power delivered by the source Vg?

Homework Equations


Ohm's Law (I = V/R)
Parallel Resistance Formula (R1 + R2*R3/R2+R3)

The Attempt at a Solution


I was able to configure the Parallel Resistance Formula correctly (I think) using the figure drawn with this problem. After that, I did the following:
Total V = 55 V (Vg... Given)
Total R = R1 + R2*R3/R2+R3 = 1083/102 = 10.62 Ohm (Formula Above)
Initial I = V/R = 55/10.62 = 5.18 A (Or I1)

then V=(I1)*(R1) across the first resistor to find V at the node = 15.54 V
I2 = that V/R2
I3 = I1-I2
and V3 = I3R3

And so forth. My I2, however, is not showing up as the right answer. I feel like I am either missing a step, or did not setup the resistance formula correctly. Help?
 
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Welcome to PF!

Hi Kas0988! Welcome to PF! :smile:

(try using the X2 tag just above the Reply box :wink:)
Kas0988 said:
Total R = R1 + R2*R3/R2+R3 = 1083/102 = 10.62 Ohm

erm :redface: …

you've added the 3 in the wrong place! :cry:​
 

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