For determination of resistance of a coil, which of two methods is better Ohm's law method or meter bridge method ?

Explanation

To determine which method is better for finding the resistance of a coil between the Ohm's law method and the meter bridge method, we can analyze both methods step by step.

### Step-by-Step Solution:

1. **Understanding Ohm's Law Method:**
- Ohm's law states that \( V = IR \), where \( V \) is the voltage, \( I \) is the current, and \( R \) is the resistance.
- To find the resistance of a coil using this method, we rearrange the formula to \( R = \frac{V}{I} \).
- We need to measure the voltage across the coil and the current flowing through it.

2. **Setting Up the Circuit:**
- Connect the coil in series with a known resistance \( R \).
- Use an ammeter to measure the current \( I \) flowing through the circuit.
- Connect a voltmeter in parallel with the coil to measure the voltage \( V \) across it.

3. **Limitations of the Ohm's Law Method:**
- The ammeter and voltmeter have their own resistances, which can affect the measurements.
- The presence of these resistances can lead to inaccurate readings of current and voltage, thus affecting the calculated resistance \( R \).

4. **Understanding Meter Bridge Method:**
- The meter bridge method is based on the principle of a null point in a Wheatstone bridge configuration.
- An unknown resistance \( X \) is connected in series with a known resistance \( R \) on a bridge wire.

5. **Setting Up the Meter Bridge:**
- Connect the known resistance \( R \) and the unknown resistance \( X \) on the meter bridge.
- Use a jockey to find the null point where the galvanometer shows zero current.

6. **Calculating Resistance Using Meter Bridge:**
- At the null point, the ratio of the resistances is given by the balance point equation:
\[ \frac{R}{X} = \frac{100 - L}{L} \]
- Here, \( L \) is the length of the wire from one end to the null point, and \( 100 - L \) is the remaining length.

7. **Advantages of the Meter Bridge Method:**
- The meter bridge method is more sensitive and provides more accurate results because it does not depend on the current flowing through the galvanometer.
- The resistance values obtained are absolute and not affected by the resistances of the measuring instruments.

8. **Conclusion:**
- After comparing both methods, the meter bridge method is determined to be better for finding the resistance of a coil due to its accuracy and sensitivity.

### Final Answer:
The meter bridge method is better than the Ohm's law method for determining the resistance of a coil.

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