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Lecture

Apparent and True Power: Transformer

In course

PHYS-201(d): General physics: electromagnetism

The topics covered by the course are concepts of electromagnetism, properties of waves, and fluid mechanics. ...

Description

This lecture covers the concepts of apparent and true power in electrical circuits, focusing on the power factor and power triangle. It explains how to calculate power in circuits with resistors and inductors, emphasizing the difference between apparent and true power. The instructor discusses the importance of power factor in optimizing circuit efficiency and introduces the concept of time-averaging power. Additionally, the lecture explores transformers without load resistors, analyzing emfs and currents in primary and secondary circuits. It concludes with a detailed explanation of transformers with load resistors, highlighting the role of resistance in power loss.

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Instructor

Dirk Grundler

Official source

Ontological neighbourhood

Physics

Electromagnetism: Electrical networks

Electrical engineering

Power engineering: Electric power transmission

Related concepts (32)

Power factor

In electrical engineering, the power factor of an AC power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit. Real power is the average of the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the product of RMS current and voltage.

AC power

In an electric circuit, instantaneous power is the time rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the direction of energy flow. Its SI unit is the watt. The portion of instantaneous power that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as instantaneous active power, and its time average is known as active power or real power.

Transformer

A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits.

Resistor

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat may be used as part of motor controls, in power distribution systems, or as test loads for generators.

Electric power

Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions of watts are called kilowatts, megawatts and gigawatts respectively. A common misconception is that electric power is bought and sold, but actually electrical energy is bought and sold.

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