Wheatstone's bridge cannot be used for measurnment of very ………….. Resistance.

Options

A. high
B. low
C. high
D. zero

Answer

### Step-by-Step Solution:

1. **Understanding Wheatstone Bridge**:
The Wheatstone bridge is a circuit used to measure unknown electrical resistances by balancing two legs of a bridge circuit. It consists of four resistors, a voltage source, and a galvanometer.

2. **Identifying the Limitation**:
The Wheatstone bridge is particularly effective for measuring resistances that are within a certain range. However, it has limitations when it comes to measuring very low resistances.

3. **Reason for Limitation**:
When the resistance is very small (for example, in the micro-ohm range), the balancing of the bridge becomes difficult. This is because the galvanometer may not show a clear zero deflection due to the small voltage drop across the unknown resistance.

4. **Practical Example**:
If we consider an example where the known resistance is 1 kΩ and the unknown resistance is 1 µΩ (micro-ohm), achieving a balance becomes impractical. The physical limitations of the apparatus and the sensitivity of the galvanometer make it nearly impossible to measure such small values accurately.

5. **Conclusion**:
Therefore, the Wheatstone bridge cannot be used for the measurement of very low resistances, specifically those in the micro-ohm range.

### Final Answer:
Wheatstone's bridge cannot be used for the measurement of very **low resistance**.

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