In a metre bridge experiment (as shown in figure), the positions of the cell E, and galvanometer G, are interchanged. We shall observe in the galvanometer: ____.
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This property is known as the "Principle of Conjugate Arms." It implies that the sensitivity of the bridge might change after interchanging, but the balance point remains at the same location.
Both right-sided and left-sided deflection and at balance point, no deflection
Only the right-sided deflection
There will be no deflection irrespective of the position of the jockey
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The Correct Option isB
Solution and Explanation
Step 1: Understanding the Topic:
This question covers "Current Electricity" and the operational theory of the "Wheatstone Bridge," upon which the metre bridge is based. A key property of the Wheatstone bridge is its symmetry. The four resistors, the galvanometer, and the power source form a network where certain components can be swapped without destroying the balance condition. Step 2: Key Formulas and Approach:
The Wheatstone balance condition is $R_1/R_2 = R_3/R_4$. In this state, the points where the galvanometer is connected are at the same potential. Step 3: Detailed Explanation:
The Conjugate Property: In a Wheatstone bridge, the arms containing the battery and the galvanometer are called "conjugate arms." If the bridge is balanced, interchanging the battery and the galvanometer does not change the balance condition.
Experiment behavior: Even after interchanging E and G, as we slide the jockey along the wire, we are changing the ratio of the resistances of the two segments of the wire.
Deflection: When the jockey is to the left of the balance point, the bridge is unbalanced in one direction, causing the galvanometer to deflect (e.g., to the left).
When the jockey is to the right of the balance point, the bridge is unbalanced in the opposite direction, causing a right-sided deflection.
At the exact same balance point as before, the potential difference across the galvanometer remains zero, resulting in no deflection.
Step 4: Final Answer:
The observer will see both-sided deflections and no deflection at the balance point.
