Resistors and heat — desirability of power dissipation: In general-purpose electronics (excluding heaters and special cases), is the heat produced by a resistor a desirable effect, or is it usually an unwanted loss?

Introduction / Context:
Resistors convert electrical energy into heat through Joule heating. While some applications deliberately use resistors as heaters or current limiters, the overwhelming majority of circuits aim to deliver power to loads like ICs, motors, or LEDs, not to waste it in resistors. This question checks whether heating is generally considered beneficial or undesirable in typical designs.

Given Data / Assumptions:

• Every resistor dissipates P = I^2 * R = V^2 / R = V * I.
• Ordinary circuits aim for efficiency, reliability, and thermal safety margins.
• Specialized heater or inrush-limiter roles are not the default case.

Concept / Approach:
In most designs, heat in resistors is wasted energy that stresses components and raises ambient temperature. Excess heat can shift values (temperature coefficient), accelerate aging, and require larger enclosures or heatsinks. Therefore the statement “Heat produced by a resistor is generally a desirable effect” is false in the general case. Designers size resistor wattage to tolerate unavoidable dissipation while minimizing it by using higher efficiency topologies (e.g., switching regulators instead of large series drop resistors).

Step-by-Step Solution:

Verification / Alternative check:
Thermal derating curves and resistor power ratings exist precisely because overheating is harmful. Engineers check that P_diss < P_rating and often prefer low-loss solutions to keep temperatures down.

Why Other Options Are Wrong:

• Correct: Not correct; typical circuits avoid unnecessary heat.
• Only desirable in power wirewound resistors / PTC thermistors: While there are niche uses involving heat, the question asks about general practice—where heating is not desirable.

Common Pitfalls:
Generalizing from special heater applications; ignoring that even in current limiting, the heat is tolerated, not sought for its own sake.

Final Answer:
Incorrect.