Kirchhoff's Laws & Circuits
Current Electricity
64
JEE Qs
12%
Hard
75
min
Systematic application of KVL sign conventions, careful choice of independent loops, and meticulous algebraic solving are crucial for success in Kirchhoff's Laws problems.
🧮 Key Formulas
✅ Key Points for JEE
- 1Master the sign conventions for KVL consistently: potential rise (+), potential drop (-). For a resistor, potential drops when traversing in the direction of current, and rises when traversing opposite to current.
- 2KCL is based on the conservation of charge; KVL is based on the conservation of energy.
- 3Assign current directions arbitrarily. If the calculated current is negative, its actual direction is opposite to the assumed one.
- 4Identify independent loops and junctions to form a system of solvable linear equations. The number of independent KVL equations is b - j + 1, where b is the number of branches and j is the number of junctions.
- 5Always consider the internal resistance of batteries/cells in KVL calculations if provided, as it affects the terminal voltage.
⚠️ Common Mistakes
- ✕Errors in applying KVL sign conventions, especially confusing potential drop/rise across resistors and cells.
- ✕Not identifying sufficient independent loops or choosing redundant loops, leading to an unsolvable or overdetermined system of equations.
- ✕Forgetting to include the internal resistance of batteries in KVL equations, leading to incorrect current and voltage calculations.
- ✕Incorrectly applying series/parallel reduction techniques to circuits where Kirchhoff's laws are necessary, or conversely, using KVL where simpler reduction is possible.
📝 Practice Questions
See allQ47.The value of current I in the electrical circuit as given below, when potential at A is equal to the potential at B, will be ____ A.
Q27.Given below are two statements : Statement-I : The equivalent emf of two nonideal batteries connected in parallel is smaller than either of the two emfs. Statement-II : The equivalent internal resistance of two nonideal batteries connected in parallel is smaller than the internal resistance of either of the two batteries. In the light of the above statements, choose the correct answer from the options given below. (1) Both Statement-I and Statement-II are false (2) Statement-I is false but Statement-II is true (3) Both Statement-I and Statement-II are true (4) Statement-I is true but Statement-II is false
Q34. Sliding contact of a potentiometer is in the middle of the potentiometer wire having resistance Rp = 1Ω as shown in the figure. An external resistance of Re = 2Ω is connected via the sliding contact. The electric current in the circuit is : (1) 0.9 A (2) 1.35 A (3) 0.3 A (4) 1.0 A 2025 (22 Jan Shift 1) JEE Main Previous Year Paper
Q45.Which of the following resistivity ( ρ ) v/s temperature (T) curves is most suitable to be used in wire bound standard resistors? (1) (2) (3) (4)
Q47.The net current flowing in the given circuit is_______ A.
Q30.Refer to the circuit diagram given in the figure. which of the following observations are correct? A. Total resistance of circuit is 6Ω B. Current in Ammeter is 1 A C. Potential across AB is 4 Volts. D. Potential across 2025 (23 Jan Shift 1) JEE Main Previous Year Paper CD is 4 Volts E. Total resistance of the circuit is 8Ω. Choose the correct answer from the options given below: (1) A, B and D Only (2) A, B and C Only (3) A, C and D Only (4) B, C and E Only
NCERT Chapters
- Class 12 Physics Ch 3: Current Electricity