Wheatstone Bridge is not suitable for measurement of

Options

A. very high value resistances.
B. very low value resistances.
C. both (A) and (B).
D. medium value resistances.

Explanation

To determine the suitability of the Wheatstone Bridge for measuring different values of resistance, we need to analyze the characteristics of the bridge and how it interacts with various resistance values.

### Step-by-Step Solution:

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

2. **Measurement of Very Low Resistance**:
- When measuring very low resistances (e.g., less than 1 ohm), the lead resistances (the resistance of the connecting wires) become significant compared to the low resistance being measured.
- For example, if the resistance is 0.5 ohms and the lead resistance is 0.02 ohms, the lead resistance can introduce a significant error (2% or more).
- This error can lead to inaccurate measurements, making the Wheatstone Bridge unsuitable for very low resistances.

3. **Measurement of Very High Resistance**:
- For very high resistances, the current flowing through the circuit becomes very small due to Ohm's law (I = V/R).
- A high resistance can cause the deflection in the galvanometer to be negligible, making it difficult to obtain a clear reading.
- If the resistance is too high, the current may be so low that it does not produce a measurable deflection in the galvanometer, rendering the Wheatstone Bridge ineffective for high resistance measurements.

4. **Conclusion**:
- The Wheatstone Bridge is not suitable for measuring both very low and very high resistances. It is most effective for medium-range resistances where the effects of lead resistance and galvanometer sensitivity are optimal.

5. **Correct Answer**: Therefore, the Wheatstone Bridge is not suitable for measurement of **both very high and very low resistance**.