Resistor taxonomy in electronics: What are the two major categories into which resistors are broadly classified for circuit design and selection?

Introduction / Context:
Resistors are ubiquitous passive components that set currents, divide voltages, and shape time constants. For selection, engineers first distinguish between fixed-value parts and adjustable parts. This high-level categorization influences footprint, tolerance, adjustability, and use cases such as calibration or user control.

Given Data / Assumptions:

• We are discussing everyday components used on printed circuit boards and instruments.
• Focus on functional categories rather than specific technologies (carbon film, metal film, wirewound, thick film).
• Variable devices include both manually adjustable and electronically variable forms.

Concept / Approach:
Fixed resistors have a single nominal value specified by tolerance (for example, 10 kΩ ± 1%). Variable resistors can be adjusted: potentiometers provide a variable divider; rheostats provide a variable series resistance; trimmers allow board-level calibration. This functional split determines whether the circuit can be tuned after assembly or must rely on component tolerance alone.

Step-by-Step Solution:

Verification / Alternative check:
Look at distributor catalogs: filters typically offer ”fixed resistors” and ”potentiometers/trimmers” as primary families, reinforcing this classification across manufacturers.

Why Other Options Are Wrong:

• Low/high ohmic value or power value: These are parametric ranges, not fundamental categories.
• Commercial/industrial: Refers to quality or environmental rating, not function.

Common Pitfalls:
Confusing potentiometer wiring: a potentiometer can be used as a voltage divider (three terminals) or as a rheostat (two terminals), but both are still variable resistors.

Final Answer:
fixed and variable