Resistor of resistance `20Omegaand 30 Omega` are joined in series a battery of emf 3V . It is desired to measure current and voltage across the `20Omega` resistor with the help of an ammeter and a voltmeter. Identify the correct arrangement of ammeter (A) and voltmeter (V) out of four possible arrangement shown in the figure given below.

Options

A.
B.
C.
D.

Answer

To solve the problem of measuring the current and voltage across a 20 Ω resistor in a series circuit with a 30 Ω resistor and a 3V battery, we need to understand the correct arrangement of the ammeter and voltmeter.

### Step-by-Step Solution:

1. **Understand the Circuit Configuration**:
- We have two resistors: 20 Ω and 30 Ω connected in series with a 3V battery.
- In a series circuit, the same current flows through all components.

2. **Identify the Function of the Ammeter and Voltmeter**:
- The **ammeter** is used to measure the current flowing through the circuit. It must be connected in series with the component whose current we want to measure.
- The **voltmeter** is used to measure the voltage across a specific component. It must be connected in parallel with that component.

3. **Connect the Ammeter**:
- Since we want to measure the current through the 20 Ω resistor, the ammeter should be connected in series with the 20 Ω resistor. This ensures that the current flowing through the resistor is the same as the current measured by the ammeter.

4. **Connect the Voltmeter**:
- To measure the voltage across the 20 Ω resistor, the voltmeter should be connected in parallel with the 20 Ω resistor. This allows the voltmeter to measure the potential difference across the resistor.

5. **Evaluate the Possible Arrangements**:
- Out of the four possible arrangements shown in the figure, we need to identify the one where the ammeter is in series with the 20 Ω resistor and the voltmeter is in parallel with the same resistor.

6. **Conclusion**:
- The correct arrangement will have the ammeter in series with the 20 Ω resistor and the voltmeter in parallel with the 20 Ω resistor. This arrangement allows for accurate measurement of both current and voltage.

### Final Answer:
The correct arrangement is where the ammeter (A) is connected in series with the 20 Ω resistor and the voltmeter (V) is connected in parallel with the 20 Ω resistor.