Sähköresistanssia

Sähköresistanssia, often simply referred to as resistance, is a fundamental property of an electrical conductor that quantifies how much it opposes the flow of electric current. It is the opposition to the movement of charged particles, typically electrons, through a material. The SI unit for electrical resistance is the ohm, symbolized by the Greek letter omega (Ω).

Resistance is influenced by several factors. Firstly, the material's intrinsic property, known as resistivity, plays a significant role. Materials with high resistivity, such as rubber or glass, are good insulators and resist current flow strongly. Conversely, materials with low resistivity, like copper or silver, are excellent conductors and offer little resistance. Secondly, the length of the conductor is directly proportional to its resistance; a longer wire will have more resistance than a shorter one of the same material and cross-sectional area. Thirdly, the cross-sectional area of the conductor is inversely proportional to its resistance; a thicker wire has less resistance than a thinner one. Finally, temperature also affects resistance. For most conductors, resistance increases with increasing temperature due to increased atomic vibrations hindering electron flow.

Ohm's Law describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit: V = I * R. This law states that the voltage across a conductor is directly proportional to the current flowing through it, provided the resistance remains constant. Resistance dissipates electrical energy as heat, a phenomenon known as Joule heating, which has both beneficial applications, like in heating elements, and undesirable consequences, such as energy loss in transmission lines.