DCresistanssi

DCresistanssi, or direct-current resistance, is the opposition offered by an electrical element to the flow of direct current. It is measured in ohms (Ω) and denoted by R. In a circuit carrying steady direct current, the voltage and current satisfy Ohm's law: V = I · R, so R = V / I. DCresistanssi reflects the resistive, non-reactive part of an element's impedance at direct current.

For a uniform conductor, R = ρ L / A, where ρ is the material's resistivity, L is length, and A is cross-sectional area. Temperature and material properties influence R; metals have positive temperature coefficients, meaning R increases with temperature, while some carbon-based materials can behave differently. The temperature dependence is often written as R(T) = R0 [1 + α (T − T0)], with α the temperature coefficient.

Nonlinear or non-ohmic devices show DC characteristics where resistance is not constant; for example, diodes and transistors have DC resistance that changes with applied voltage or current, while resistors are designed to approximate a constant DC resistance.

Measurement and usage: DC resistance is measured with a powered-off circuit using a multimeter in resistance mode; in precision or low-resistance cases, a four-wire (Kelvin) method reduces contact and lead resistance. In design, DCresistanssi helps calculate current, voltage drop, and power dissipation: P = I^2 R or P = V^2 / R.

Applications include resistor specification, wiring design, battery and power-supply analysis, and quality control to verify component integrity. Variations in DCresistanssi over temperature or aging can affect performance and safety.