NEET Physics MCQ Quiz - Kirchhoff's Rules
Circuit Diagram Reference:
A → (4Ω) → B → (2Ω) → C → (1Ω) → A
A → (I₁-I₂) → D → (I₂+I₃-I₁) → C
B → (I₂+I₃) → D → (5V) → E → B
Key steps for solving:
- Apply Kirchhoff's junction rule at all nodes
- Apply Kirchhoff's loop rule to three independent loops
- Solve the resulting system of equations
Loop ADCA: 7I₁ - 6I₂ - 2I₃ = 10
Loop ABCA: I₁ + 6I₂ + 2I₃ = 10
Loop BCDEB: 2I₁ - 4I₂ - 4I₃ = -5
Correct Answer: A
The correct currents are:
- I₁ = 2.5A (5/2 A)
- I₂ = 5/8 A (0.625A)
- I₃ = 15/8 A (1.875A)
These values satisfy all three loop equations simultaneously:
- 7(2.5) - 6(0.625) - 2(1.875) = 17.5 - 3.75 - 3.75 = 10
- 2.5 + 6(0.625) + 2(1.875) = 2.5 + 3.75 + 3.75 = 10
- 2(2.5) - 4(0.625) - 4(1.875) = 5 - 2.5 - 7.5 = -5
Why others are wrong:
B) These values don't satisfy all three loop equations simultaneously.
C) These are approximate values but don't solve the equations exactly.
D) These values are exactly half of the correct solution.
Correct Answer: B - The current through branch AB is I₂ = 5/8 A = 0.625 A.
Why others are wrong:
A) 0.5 A is close but not the exact calculated value.
C) 1.875 A is the value of I₃, not I₂.
D) 2.5 A is the value of I₁, the main current.
Correct Answer: B - The current through AD is I₁ - I₂ = 2.5 - 0.625 = 1.875 A. Voltage drop V = IR = 1.875 × 4 = 7.5 V.
Why others are wrong:
A) 5 V is the voltage of the battery in branch DEB.
C) 10 V is the total voltage of the main battery.
D) 12.5 V is not calculated from any relevant current in this circuit.
