Voltmeter reading in mixed networks: In a series–parallel DC circuit powered by an 18 V source, a correctly connected ideal voltmeter placed directly across the source terminals should indicate 18 V (ignoring wiring drops and meter loading). Decide whether this statement is accurate.

Introduction / Context:
Knowing what a voltmeter should read in a practical series–parallel circuit is fundamental to troubleshooting. When you connect a voltmeter across the supply terminals, you are measuring the source's terminal voltage. If the DC source is specified as 18 V and loading effects are negligible, the reading should be 18 V. This question checks recognition of proper measurement placement and the definition of terminal voltage.

Given Data / Assumptions:

• DC source nominal value: 18 V.
• Voltmeter is ideal (very high input resistance), connected directly across the source terminals.
• Lead resistance and wiring drops are negligible for the concept check.
• No meter misconfiguration or wrong range selection.

Concept / Approach:
Voltage is the potential difference between two points. Terminal voltage of a source is the potential difference at its output terminals. An ideal voltmeter has nearly infinite resistance, so it draws negligible current and does not appreciably alter the circuit. Therefore it reports the source terminal voltage, which equals the rated value in this idealized scenario.

Step-by-Step Solution:

Verification / Alternative check:
Measure any component in parallel with the source; it will also show approximately 18 V in an ideal model. Bench experiments with a DMM (10 MΩ input) typically read the nominal source value within tolerance.

Why Other Options Are Wrong:

• Incorrect: Conflicts with the definition of terminal voltage.
• Valid only with an analog meter: Digital or analog does not change the physics.
• True only if load current is zero: Finite load current does not change an ideal measurement.
• Depends on lead polarity: Polarity affects sign, not magnitude; meters auto-range absolute value in DC volts mode when leads are swapped.

Common Pitfalls:
Putting the voltmeter in series (that would be an ammeter position), measuring at the wrong nodes, or expecting internal source resistance drops without modeling them explicitly.

Final Answer:
Correct