15.1 AC Sources
2 min read•june 24, 2024
Alternating_current_(ac)0### is the lifeblood of our modern electrical grid. Unlike ###Direct_current(dc)_0###, AC periodically reverses direction, allowing for efficient power transmission over long distances and easy voltage transformation.
AC sources produce sinusoidal waveforms characterized by , , and . Understanding these properties is crucial for analyzing AC circuits, calculating power, and working with electromagnetic devices like transformers in our everyday electrical systems.
Alternating Current (AC) Sources
DC vs AC characteristics
Top images from around the web for DC vs AC characteristics
Alternating Current versus Direct Current | Physics View original
Is this image relevant?
DC vs. AC ~ NEW TECH View original
Is this image relevant?
Alternating Current versus Direct Current | Physics View original
Is this image relevant?
Alternating Current versus Direct Current | Physics View original
Is this image relevant?
DC vs. AC ~ NEW TECH View original
Is this image relevant?
1 of 3
Top images from around the web for DC vs AC characteristics
Alternating Current versus Direct Current | Physics View original
Is this image relevant?
DC vs. AC ~ NEW TECH View original
Is this image relevant?
Alternating Current versus Direct Current | Physics View original
Is this image relevant?
Alternating Current versus Direct Current | Physics View original
Is this image relevant?
DC vs. AC ~ NEW TECH View original
Is this image relevant?
1 of 3
- (DC) flows continuously in a single direction maintains a constant voltage polarity commonly used in batteries and solar cells
- (AC) periodically reverses direction voltage polarity alternates between positive and negative follows a commonly used in power outlets and generators
Key features of AC waveforms
- Amplitude represents the maximum voltage or current reached during a cycle measured in volts (V) for voltage and amperes (A) for current
- Frequency () indicates the number of cycles per second measured in (Hz) calculated using where is the or time for one complete cycle
- Phase describes the relative position of a waveform compared to a reference measured in degrees () or radians (rad)
- waveforms align at their peaks and troughs (AC voltage and current in a resistive circuit)
- waveforms do not align at their peaks and troughs (AC voltage and current in capacitive or inductive circuits)
- Phasors are used to represent the magnitude and phase of AC quantities graphically
RMS values in AC circuits
- () values represent the effective value of an AC voltage or current equivalent to the DC value that would produce the same heating effect commonly used to compare AC and DC quantities
- RMS voltage () for a sinusoidal waveform calculated using where is the maximum voltage reached during a cycle (120 V RMS in US households)
- RMS current () for a sinusoidal waveform calculated using where is the maximum current reached during a cycle (10 A RMS in a typical household circuit)
AC Circuit Analysis
- is the total opposition to current flow in an AC circuit, combining resistance and
- Reactance is the opposition to current flow due to inductors and capacitors in AC circuits
- represents the ratio of real power to apparent power in AC circuits
- occurs when inductive and capacitive reactances cancel out, resulting in maximum power transfer
Electromagnetic Devices in AC Systems
- Transformers use to step up or step down AC voltages for efficient power transmission and distribution
Key Terms to Review (33)
AC: AC, or alternating current, is the flow of electric charge that periodically reverses direction, in contrast to direct current (DC) where the flow of electric charge is unidirectional. AC is the standard form of electricity supplied to homes and businesses, powering a wide range of electrical devices and appliances.
Alternating Current: Alternating current (AC) is an electric current that periodically reverses direction, in contrast to direct current (DC) which flows in a constant direction. AC is the standard form of electricity distribution and is used in a wide range of applications, from powering household appliances to generating electricity in power plants.
Alternating current (ac): Alternating current (AC) is an electric current that periodically reverses direction. Unlike direct current (DC), AC voltage and current change their magnitudes continuously with time.
Ampere: An ampere (A) is the unit of electric current in the International System of Units (SI). It is defined as the flow of one coulomb of charge per second.
Ampere: The ampere (symbol: A) is the base unit of electric current in the International System of Units (SI). It is defined as the constant flow of one coulomb of electric charge per second, and it is a fundamental quantity in the study of electromagnetism and electrical circuits.
Amplitude: Amplitude refers to the maximum displacement or the peak value of a periodic waveform, such as a sine wave or a sound wave. It represents the magnitude or the size of the oscillation and is a crucial parameter in the study of wave phenomena.
Capacitive reactance: Capacitive reactance is the opposition that a capacitor offers to alternating current (AC), due to the phase difference between voltage and current. It is inversely proportional to both the frequency of the AC signal and the capacitance.
DC: DC, or direct current, is the continuous flow of electrical charge in a single direction. It is a fundamental concept in electrical systems and is contrasted with alternating current (AC), where the flow of charge periodically reverses direction.
Direct current: Direct current (DC) is the flow of electric charge in a single direction, characterized by a constant voltage level. Unlike alternating current (AC), where the voltage periodically reverses direction, DC maintains a steady voltage, making it ideal for powering electronic devices and batteries. Understanding DC is crucial when comparing it to AC sources, as it helps explain how different electrical systems operate.
Direct current (dc): Direct current (DC) is a type of electrical current where the flow of electric charge is unidirectional. It contrasts with alternating current (AC), which periodically reverses direction.
Electromagnetic Induction: Electromagnetic induction is the process by which a changing magnetic field induces an electromotive force (EMF) in a conductor, causing an electric current to flow. This phenomenon is fundamental to the operation of many electrical devices and is crucial in understanding the relationship between electricity and magnetism.
Frequency: Frequency is a fundamental concept in physics that describes the number of occurrences or cycles of a periodic phenomenon per unit of time. It is a crucial parameter in understanding various physical processes, including alternating current (AC) sources, power in AC circuits, electromagnetic waves, and the electromagnetic spectrum.
Hertz: Hertz (Hz) is a unit of frequency that measures the number of cycles or oscillations per second. It is a fundamental concept in the study of alternating current (AC) sources and simple AC circuits.
Impedance: Impedance is the measure of opposition that a circuit presents to the flow of alternating current (AC) at a particular frequency. It combines resistance, inductive reactance, and capacitive reactance into a single value represented as a complex number.
Impedance: Impedance is a measure of the opposition to the flow of alternating current (AC) in an electrical circuit. It encompasses the combined effects of resistance, capacitance, and inductance, and determines the overall behavior of the circuit under AC conditions.
In-Phase: In-phase refers to the state where two or more oscillating signals, such as waves or alternating current (AC) sources, are aligned and reach their maximum and minimum values at the same time. This synchronization of the signals is a crucial concept in the study of AC sources.
Irms: Irms, or root-mean-square (RMS) current, is a measure of the effective or equivalent direct current (DC) value of an alternating current (AC) waveform. It represents the magnitude of an AC signal and is the square root of the average of the square of the instantaneous current values over one complete cycle.
Magnetic resonance imaging: Magnetic Resonance Imaging (MRI) is a medical imaging technique used to visualize internal structures of the body using magnetic fields and radio waves. It relies on the principles of nuclear magnetic resonance to generate detailed images of organs and tissues.
Out-of-phase: Out-of-phase refers to a condition in which two waveforms have their peaks and troughs aligned in such a way that they are not synchronized with each other. This misalignment can lead to destructive interference, where the amplitude of one wave cancels out the amplitude of another, resulting in reduced overall amplitude. Understanding this concept is crucial for analyzing how alternating current (AC) sources behave when connected in circuits, particularly in relation to voltage and current waveforms.
Period: In the context of oscillations and waves, the period is the time taken for one complete cycle of motion or wave to occur. This concept is crucial as it relates to frequency, which is the number of cycles per second, and helps in understanding how oscillatory systems, like those in circuits or alternating current sources, behave over time.
Phase: Phase refers to the state or condition of a system, particularly in the context of periodic phenomena. It describes the relative position or timing of a waveform, such as an alternating current (AC) signal, within a complete cycle.
Phasor: A phasor is a mathematical representation of a sinusoidal function, such as an alternating current (AC) or voltage, that captures both the amplitude and the phase of the waveform. It is a powerful tool for analyzing and understanding the behavior of AC circuits and systems.
Power factor: Power factor is the ratio of real power (P) to apparent power (S) in an AC circuit. It indicates how effectively the electrical power is being converted into useful work output.
Power Factor: Power factor is a dimensionless quantity that describes the relationship between the real power and apparent power in an alternating current (AC) electrical system. It is a measure of how efficiently the load converts supplied AC power into useful work, with a value ranging from 0 to 1.
Reactance: Reactance is a measure of the opposition to the flow of alternating current (AC) in an electrical circuit, caused by the presence of inductors and capacitors. It represents the reactive component of impedance, which is distinct from the resistive component that dissipates energy as heat.
Resonance: Resonance is a phenomenon that occurs when a system is driven by a force that matches the system's natural frequency of oscillation, resulting in a dramatic increase in the amplitude of the system's response. This concept is fundamental in understanding the behavior of various physical systems, including electrical circuits, mechanical vibrations, and acoustic waves.
RMS: RMS, or Root Mean Square, is a statistical measure used to quantify the magnitude or average value of a varying quantity, such as an alternating current (AC) signal. It represents the effective or equivalent value of a waveform, providing a way to compare AC and direct current (DC) quantities.
Root Mean Square: The root mean square (RMS) is a statistical measure that quantifies the magnitude of a varying quantity, such as an alternating current (AC) or an alternating voltage. It represents the effective or equivalent value of a varying waveform, providing a way to compare the power of an AC signal to that of a direct current (DC) signal.
Sinusoidal Waveform: A sinusoidal waveform is a continuous, smooth, wave-like function that oscillates between positive and negative values in a periodic manner. This waveform is characterized by a single frequency and is commonly used to represent alternating current (AC) signals in electrical and electronic systems.
Step-down transformer: A step-down transformer is a device that reduces the voltage from the primary winding to the secondary winding while increasing the current. It operates on the principle of electromagnetic induction and follows the transformer equation.
Transformer: A transformer is a device that uses electromagnetic induction to transfer electrical energy from one circuit to another, usually to change the voltage or current levels between the two circuits. It is a fundamental component in various applications of electricity and electronics.
Volt: The volt is the unit of electric potential and electromotive force in the International System of Units (SI). It represents the potential difference across a conductor when a current of one ampere dissipates one watt of power. The volt is a fundamental unit that is essential in understanding and quantifying various electrical phenomena, from the storage of energy in capacitors to the generation of alternating current in household wiring.
Vrms: Vrms, or root-mean-square voltage, is a measure of the effective voltage of an alternating current (AC) signal. It represents the equivalent direct current (DC) voltage that would produce the same amount of power in a resistive load as the AC signal.