Passive sign convention in resistors — for a resistor carrying conventional current from one terminal to the other, the terminal where current enters is labeled positive and the terminal where current exits is labeled negative. Choose the correct polarity assignment.

Introduction / Context:
Correct polarity labeling is essential for applying Kirchhoff’s laws and for calculating power in passive components. The passive sign convention standardizes how we assign voltage polarities relative to current direction so that power absorbed by a passive element is positive when current enters its positive-labeled terminal.

Given Data / Assumptions:

• A single resistor with conventional current defined from the entry terminal to the exit terminal.
• Ideal resistor behavior (V = I * R).
• Steady-state consideration, though the convention also applies instantaneously in AC.

Concept / Approach:
Under the passive sign convention, voltage polarity across a passive element is assigned such that the terminal where current enters is marked positive. For a resistor this ensures that power P = V * I is positive when the resistor dissipates energy as heat: with V defined positive at the entry terminal and current I defined entering that terminal, P becomes positive, matching physical intuition.

Step-by-Step Solution:

Verification / Alternative check:
Measure the voltage with a meter whose red lead is at the entry side; a positive reading corresponds to a drop from entry to exit consistent with energy dissipation. Reversing the leads or current direction flips signs consistently while preserving the convention.

Why Other Options Are Wrong:

Common Pitfalls:
Mixing up active versus passive sign conventions; forgetting to keep current and voltage reference directions consistent, which leads to wrong signs in KVL/KCL equations and power calculations.

Final Answer:
Positive at entry, negative at exit