Resistiiivisyys

Resistiiivisyys, often denoted by the Greek letter rho (ρ), is an intrinsic property of a material that quantifies how strongly it resists the flow of electric current. It is a measure of how difficult it is for charge carriers, such as electrons, to move through a substance. Materials with high resistiiivisyys are called electrical insulators, while materials with low resistiiivisyys are called electrical conductors.

The resistiiivisyys of a material is independent of its shape or size, unlike electrical resistance. Electrical resistance (R) depends on both the resistiiivisyys of the material and the physical dimensions of the object. Specifically, resistance is given by the formula R = ρL/A, where L is the length of the conductor and A is its cross-sectional area. This means that a longer or thinner object made of the same material will have higher resistance.

Temperature significantly affects the resistiiivisyys of most materials. For conductors, resistiiivisyys generally increases with temperature because increased thermal vibrations of the atoms impede the movement of charge carriers. For semiconductors, the relationship is more complex, with resistiiivisyys often decreasing as temperature rises due to the creation of more charge carriers. Superconductors, at very low temperatures, exhibit zero resistiiivisyys, allowing current to flow indefinitely without energy loss. The unit of resistiiivisyys in the International System of Units (SI) is the ohm-meter (Ω·m).