sähkötehosta

Sähkötehosta, meaning "electrical power" in Finnish, refers to the rate at which electrical energy is transferred or consumed by an electrical device. It is a fundamental concept in electrical engineering and physics. The unit of electrical power is the watt (W), named after Scottish inventor James Watt. One watt is defined as one joule of energy per second.

In direct current (DC) circuits, electrical power can be calculated by multiplying the voltage across the circuit by the current flowing through it. The formula is P = V * I, where P is power, V is voltage, and I is current. For example, if a light bulb draws 0.5 amperes of current from a 120-volt source, its power consumption is 60 watts (0.5 A * 120 V = 60 W).

In alternating current (AC) circuits, the calculation of power is more complex due to the fluctuating nature of voltage and current. The instantaneous power varies continuously. However, for sinusoidal AC, the average power, often referred to as real power, is calculated using P = V_rms * I_rms * cos(θ), where V_rms and I_rms are the root-mean-square values of voltage and current, respectively, and θ is the phase angle between them. The term cos(θ) is known as the power factor. Reactive power, measured in volt-amperes reactive (VAR), also plays a role in AC systems, representing the energy that oscillates back and forth between the source and reactive components like capacitors and inductors.

Understanding sähkötehosta is crucial for designing efficient electrical systems, sizing power supplies, and ensuring the safe operation of electrical appliances. It dictates how quickly energy is used or delivered and influences factors such as heat generation and the performance of electrical equipment.