It is required to measure the equivalent resistance of a circuit with an ideal battery, ideal voltmeter & ideal ammeter. Which circuit diagram shows voltmeter V and ammeter A correctly positioned to measure the total resistance of the circuit?

Explanation

A voltmeter is always connected in parallel, and an ammeter is always connected in series. As only this option shows the correct arrangement, this is the correct answer. To measure the total (equivalent) resistance R of a circuit using:An ideal battery (known voltage V).An ideal voltmeter (infinite resistance).An ideal ammeter (zero resistance).From Ohm's Law: R=V/IWhere:V is the voltage across the whole circuit.III is the current through the whole circuit.(A) is correct because:The voltmeter is connected across the entire resistor network (measuring total voltage V).The ammeter is connected in series with the network (measuring total current III).This setup allows the correct use of Ohm's law.