Kirchhoff’s Rule Part-3

Q Find the currents in the given circuit

⚡ Find Current in Each Branch

🔍 Given Circuit

Let the branch currents be:

  • $I_1$ in the lower branch
  • $I$​ in the middle branch
  • $I_3$​ in the upper branch

Using Kirchhoff’s Current Law (KCL) at junction F:I1+I2=I3I_1 + I_2 = I_3


🔄 Loop ABCF

Applying Kirchhoff’s Loop Rule (KVL):−(I1+I2)(1)−2−2I2−1=0-(I_1+I_2)(1)-2-2I_2-1=0Expanding:−I1−I2−2−2I2−1=0-I_1-I_2-2-2I_2-1=0 −I1−3I2−3=0-I_1-3I_2-3=0

Therefore,I1+3I2=−3I_1+3I_2=-3

✅ Equation (1)


🔄 Loop ABDE

Applying KVL:−(I1+I2)(1)−2+4−2I1=0-(I_1+I_2)(1)-2+4-2I_1=0

Expanding:−I1−I2−2+4−2I1=0-I_1-I_2-2+4-2I_1=0−3I1−I2+2=0-3I_1-I_2+2=0

Therefore,3I1+I2=23I_1+I_2=2

✅ Equation (2)


✏️ Solving Equations (1) and (2)

From Equation (1):I1+3I2=−3I_1+3I_2=-3

Multiply by 3:3I1+9I2=−93I_1+9I_2=-9

Equation (2):3I1+I2=23I_1+I_2=2

Subtracting:8I2=−118I_2=-11I2=−118AI_2=-\frac{11}{8}A

✅ Current in middle branchI2=−118A\boxed{I_2=-\frac{11}{8}A}​


Substituting into Equation (2):3I1−118=23I_1-\frac{11}{8}=2 3I1=2783I_1=\frac{27}{8}I1=98AI_1=\frac{9}{8}A

✅ Current in lower branchI1=98A\boxed{I_1=\frac{9}{8}A}


🔌 Finding I3I_3

Using KCL:I3=I1+I2I_3=I_1+I_2​ I3=98−118I_3=\frac{9}{8}-\frac{11}{8}​ I3=−28I_3=-\frac{2}{8} I3=−14AI_3=-\frac{1}{4}A

✅ Current in upper branchI3=−14A\boxed{I_3=-\frac{1}{4}A}​


🎯 Final Currents

✅ Upper Branch:I3=−14A\boxed{I_3=-\frac{1}{4}A}​

✅ Middle Branch:I2=−118A\boxed{I_2=-\frac{11}{8}A}

✅ Lower Branch:I1=98A\boxed{I_1=\frac{9}{8}A}


⚡ Find Potential Difference Between A and D

Using the upper branch:VA−(−14×1)−2=VDV_A-\left(-\frac{1}{4}\times1\right)-2=V_D VA+14−2=VDV_A+\frac{1}{4}-2=V_DVA−74=VDV_A-\frac{7}{4}=V_D

Therefore,VD−VA=−74VV_D-V_A=-\frac{7}{4}V

✅ Potential difference between D and AVD−VA=−74V\boxed{V_D-V_A=-\frac{7}{4}V}

orVA−VD=74V\boxed{V_A-V_D=\frac{7}{4}V}​

🎉 Hence, the currents in all branches and the potential difference between A and D have been determined.

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