Wheatstone Bridge — Balanced condition, Metre Bridge
Current Electricity
19
JEE Qs
8%
Hard
60
min
Master how to quickly identify Wheatstone bridge configurations and consistently apply the balanced condition and Metre Bridge formula, including end corrections.
🧮 Key Formulas
✅ Key Points for JEE
- 1A Wheatstone bridge is balanced when the galvanometer shows zero deflection, implying no current flows through it and the potential difference across its terminals is zero.
- 2The balanced condition (P/Q = R/S) is powerful for determining an unknown resistance precisely from three known resistances without needing to know the current or voltage.
- 3The Metre Bridge is a practical application of the Wheatstone bridge principle, used to find the value of an unknown resistance or compare resistances.
- 4End corrections in a Metre Bridge account for non-uniformity of the wire near the ends or resistance of the connecting strips, and must be applied for accurate results if mentioned.
- 5The sensitivity of a Metre Bridge (i.e., accuracy of determining the null point) is maximum when the resistances P and Q are comparable, resulting in a null point near the center of the wire.
⚠️ Common Mistakes
- ✕Incorrectly identifying the Wheatstone bridge configuration when it is drawn in a non-standard or disguised manner.
- ✕Failing to apply end corrections in Metre Bridge problems when they are relevant, leading to errors in calculations.
- ✕Attempting to apply the balanced bridge condition (P/Q = R/S) to an *unbalanced* Wheatstone bridge, which requires the use of Kirchhoff's Laws for analysis.
📝 Practice Questions
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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