Vastuskuorma

Vastuskuorma, in electrical engineering, refers to a load whose impedance is primarily resistive. It is typically realized with a resistor or a network that behaves as a real (non-reactive) impedance, converting electrical energy into heat. The term is used to distinguish resistive loads from reactive or non-linear loads.

In DC operation, a vastuskuorma follows Ohm’s law: I = V / R, and dissipates power according to P = V^2 / R = I^2 R. In AC circuits, an ideal resistive load draws current in phase with the applied voltage, so the phase angle is zero. Real resistors have small parasitic inductance and capacitance, which can introduce minor phase shifts at higher frequencies or in RF applications, causing deviations from ideal behavior.

Common implementations include fixed resistors used as fixed loads, and variable resistive elements such as rheostats or potentiometers used to adjust the load. Dummy loads are specific resistive loads designed to safely dissipate power for testing power supplies, amplifiers, or other equipment without applying actual signals to a device under test.

Key specifications are resistance value (ohms), power rating (watts), tolerance, and temperature coefficient. Construction types include carbon film, metal film, and wirewound resistors, each with different power handling, stability, and noise characteristics. High-power vastuskuormat require adequate cooling and ventilation to prevent overheating, and ratings should be chosen with margin for safety and reliability.

Vastuskuorma provides a predictable, linear load ideal for measurements, testing, and training, and is a fundamental element in electronic circuit design and analysis.