Electrical resistivity is a property of materials that measures how strongly they resist the flow of electric current. It is defined as the resistance of a material of a specific length and cross-sectional area. The unit of electrical resistivity is ohm-meter (Ω·m), and it varies widely among different materials. For example, metals like copper have low resistivity, making them good conductors, while rubber has high resistivity, making it an insulator. The resistivity of a material can change with temperature. Generally, as temperature increases, the resistivity of conductors increases, while the resistivity of semiconductors can decrease. Understanding electrical resistivity is crucial in designing electrical circuits and selecting appropriate materials for various applications.