Here is the detailed explanation of the reading of the ideal voltmeter connected across R in the circuit shown below:
- **Understanding the Circuit**
In the given circuit, there is a resistor R connected in series with a voltage source V and an ammeter A. The ideal voltmeter is connected across the resistor R.
- **Voltmeter Reading**
Since the ideal voltmeter has infinite resistance, it draws no current from the circuit. As a result, the entire voltage drop across the resistor R will be measured by the voltmeter. Therefore, the reading on the voltmeter will be equal to the voltage across the resistor R, which is the same as the voltage of the voltage source V.
- **Explanation**
When a voltmeter is connected in parallel across a component in a circuit, it measures the potential difference across that component. In this case, the resistor R is the component across which the voltmeter is connected. Since an ideal voltmeter has infinite resistance, no current flows through it, and it does not affect the circuit. Therefore, the reading on the voltmeter will directly show the voltage across the resistor R.
- **Conclusion**
In conclusion, the reading of the ideal voltmeter connected across R in the given circuit will be equal to the voltage of the voltage source V. This is because the ideal voltmeter measures the voltage across the resistor R without drawing any current from the circuit.