highresistance

High resistance refers to a property of a component or material that strongly opposes the flow of electric current. In electrical engineering, resistance is measured in ohms and is a key parameter in circuit design. Components with high resistance include insulators, high-value resistors, and devices where only tiny currents are intended to flow. The designation "high" is relative; in many circuits, resistances from kiloohms to gigaohms are considered high, especially where devices require high input impedance or low leakage.

High resistance can arise from intrinsic material properties, such as high resistivity, long or narrow conductive paths, or poorly doped semiconductors. Surface leakage across insulators and moisture can also reduce effective resistance. Temperature and humidity influence resistance: metals typically increase resistance with temperature, while semiconductors may have a positive or negative temperature coefficient; contaminants and aging can further change resistance over time.

In practice, high resistance is used to limit current, form voltage dividers, set bias points, and create high-impedance input stages in measurement instruments and amplifiers. It is also a characteristic of electrical insulation, where high insulation resistance is desired to minimize leakage currents and energy loss.

Measuring high resistance requires specialized techniques because of very small currents and potential leakage paths. Test equipment may use high test voltages, guarding, or Kelvin connections to improve accuracy. Designers must consider leakage paths, insulation integrity, and the influence of environment when specifying high-resistance components or systems.