Case: Read the passage and answer the question.
Kirchhoff’s first law applies to currents at a junction in a circuit. It states that at a junction in an electrical circuit, the sum of the currents flowing into the junction is equal to the sum of the currents flowing out of the junction. Kirchhoff’s second law, also known as Kirchhoff’s voltage law, states that the sum of all the voltages around a closed loop in any circuit must be equal to zero. This follows from conservation of energy. The Wheatstone bridge, also known as the resistance bridge, is used to find an unknown resistance by balancing two legs of the bridge circuit; it works on Kirchhoff’s laws.
Which of the following works on the principle of the Wheatstone bridge?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Meter bridge
Option (1) Meter bridge — Correct. In a Wheatstone bridge the unknown resistance is found from the balance condition, when the galvanometer shows a null deflection. The meter bridge is the practical device built on this principle. In it, the unknown resistance is found by balancing the bridge.
Option (2) Voltmeter — Incorrect. A voltmeter is a galvanometer with a large resistance in series. It is connected in parallel with a section of the circuit. It reads the potential difference from the deflection of its coil, and no balanced bridge is used.
NCERT (2026-27):
Wheatstone Bridge – “The Wheatstone bridge and its balance condition provide a practical method for determination of an unknown resistance. … A practical device using this principle is called the meter bridge.”