Lastwiderstand

Lastwiderstand, or load resistor, is an electrical component that provides a defined opposition to current in a circuit, converting electrical energy into heat. In German-language contexts the term is common; in English-language electronics it is usually referred to as a load resistor or resistive load. The primary function is to simulate real-world loads, allowing sources, power supplies, amplifiers, or measurement circuits to operate under known impedance conditions.

Load resistors are used in testing and calibration, to drain battery charge, to form bleeder circuits, to create defined loads for power-supply regulation, and in RF testing as dummy loads. They help verify performance, stability, and regulation under controlled conditions.

Materials and types vary by power and environment. Fixed resistors come in many forms, from small carbon film devices rated at fractions of a watt to high-wattage wirewound or metal-oxide resistors rated at tens or hundreds of watts. For adjustable loading, rheostats or electronic loads provide variable resistance and dynamic control.

Calculations and selection hinge on power dissipation and impedance. Power rating is determined by P = V^2/R = I^2*R; the resistor must handle the expected dissipation with headroom for ambient temperature and cooling. In RF applications, dummy loads are designed to present a precise impedance, usually 50 ohms, and must withstand high peak power without significant parasitics.

Safety and handling considerations include adequate cooling, proper mounting, and insulation, especially for high-voltage or high-power installations. Lastwiderstände are common, versatile components in test benches, power electronics, and laboratory measurement setups.