Voltage is relative: Is the voltage at one point in a circuit always measured with respect to another reference point? Clarify the meaning of “voltage at a node” by considering reference selection (e.g., ground).

Introduction / Context:
Voltage is not an absolute quantity; it is the electrical potential difference between two points. This question checks understanding of reference selection (ground) and why voltmeters have two terminals.

Given Data / Assumptions:

• Any practical measurement uses a two-terminal instrument (voltmeter, oscilloscope probe with ground clip).
• The circuit may or may not be earthed; a local reference (circuit common) still exists.
• Applies to both DC and AC analysis.

Concept / Approach:

“Voltage at node A” implicitly means “voltage of node A relative to a defined reference node,” commonly called ground (0 V). Without specifying the second point, the phrase is incomplete. Instruments measure potential difference: V_AB = potential(A) − potential(B).

Step-by-Step Solution:

Verification / Alternative check:

On an oscilloscope, moving the ground clip changes the displayed “zero” baseline because the reference changes. SPICE simulations also require selecting a reference node for nodal analysis to compute node voltages.

Why Other Options Are Wrong:

• “False” assumes voltage is absolute; it is not.
• Limiting the principle to DC or only across passive components is incorrect; potential difference is universal.
• Earth ground is optional; a floating system still measures voltages relative to a chosen reference node.

Common Pitfalls:

Confusing “ground” with safety earth. In many devices, circuit common is isolated and chosen for analysis without earth bonding.

Final Answer:

True