Name: rl circuit decay after source removal
Uploaded: 2024-04-11T12:48:43.000Z
Duration: 1 min 14 s
Channel: JoVE

Gdy źródło prądu stałego zostanie nagle odłączone od obwodu RL, staje się bezźródłowe.
Zakładając, że cewka indukcyjna ma prąd początkowy i0, można określić energię początkową zmagazynowaną w cewce indukcyjnej.
Zastosowanie prawa napięcia Kirchhoffa wokół pętli i podstawienie napięć na cewce indukcyjnej i rezystorze daje równanie różniczkowe pierwszego rzędu.
Zmiana kolejności terminów, całkowanie i stosowanie granic daje równanie logarytmiczne.
Biorąc pod uwagę wykładniczą po obu stronach, określa się ostateczny wyraz naturalnej odpowiedzi obwodu.
Wykres prądu w funkcji czasu pokazuje wykładniczy spadek prądu początkowego.
Odpowiedź prądowa może być wyrażona za pomocą stałej czasowej, która jest stosunkiem indukcyjności do rezystancji.
Wyrażenie prądu służy do określenia napięcia i mocy rozpraszanej na rezystorze.
Integracja mocy rozproszonej w czasie zapewnia wyraz energii pochłoniętej przez rezystor.
Gdy czas zbliża się do nieskończoności, energia pochłonięta przez rezystor zbliża się do energii początkowej zmagazynowanej w cewce indukcyjnej, co oznacza, że energia początkowa jest stopniowo rozpraszana w rezystorze.

obwód rl bez źródła

Kiedy źródło prądu stałego zostanie nagle odłączone od obwodu RL (rezystor-cewka), obwód staje się wolny od źródła. Zakładając, że induktor ma prąd początkowy oznaczony jako I0, można wyznaczyć początkową energię zmagazynowaną w cewce.

Zastosowanie napięciowego prawa Kirchhoffa w pętli obwodu oraz podstawienie napięć na induktorze i rezystorze prowadzi do równania różniczkowego rzędu pierwszego. Przekształcenie tego równania, jego całkowanie oraz zastosowanie odpowiednich granic prowadzi do uzyskania równania logarytmicznego. Podniesienie obu stron tego równania do wykładnika pozwala otrzymać końcowe wyrażenie opisujące naturalną odpowiedź obwodu.

Jeśli wykreślimy prąd w funkcji czasu, obserwujemy wykładniczy spadek prądu początkowego. To zachowanie można wyrazić w stałej czasowej, która dla obwodu RL jest stosunkiem indukcyjności do rezystancji. Ta stała czasowa reprezentuje prędkość, z jaką obwód reaguje na zmiany sygnału wejściowego.

Korzystając z wyrażenia na prąd, można obliczyć napięcie na rezystorze i moc rozpraszaną na rezystorze. Moc rozproszona to zasadniczo szybkość utraty energii w postaci ciepła.

Aby znaleźć całkowitą energię pochłoniętą przez rezystor, rozpraszana moc jest całkowana w czasie. Gdy czas zbliża się do nieskończoności, energia pochłaniana przez rezystor zbliża się do początkowej energii przechowywanej w cewce indukcyjnej. Oznacza to, że początkowa energia zmagazynowana w cewce indukcyjnej stopniowo rozprasza się w rezystorze, aż do wyczerpania energii cewki indukcyjnej.

Podsumowując, zrozumienie zachowania obwodów RL po usunięciu źródła prądu stałego zapewnia cenny wgląd w przejściową reakcję tych obwodów. Wiedza ta ma znaczenie przy projektowaniu i analizowaniu obwodów w zastosowaniach takich jak elektronika mocy i systemy komunikacyjne, gdzie cewki indukcyjne są szeroko stosowane do filtrowania lub kształtowania sygnałów.

Obwód RL bez źródła

Gdy źródło prądu stałego zostanie nagle odłączone od obwodu RL, staje się bezźródłowe.
Zakładając, że cewka indukcyjna ma prąd początkowy i0, energia początkowa ...

Education

JoVE Core

Electrical Engineering

Elektrotechnika

Unit 1

Jednostka 1

First and Second-Order Circuits

Obwody pierwszego i drugiego rzędu

KEY TERMS AND CONCEPTS

KLUCZOWE TERMINY I POJĘCIA

RL Circuit without Source

rl circuit decay after source removal

An RL circuit begins to decay after the DC source is removed. At that moment, the circuit becomes source-free. If the inductor has an initial current, I0, it also stores initial energy. That stored energy drives the natural response of the circuit.

Kirchhoff’s voltage law is applied around the loop. The inductor voltage and resistor voltage are substituted into the equation. This gives a first-order differential equation for the current. Rearranging the terms produces a logarithmic form, which can then be integrated with limits. Taking the exponential of both sides gives the final current expression.

The current decreases exponentially with time. This drop can be described with the time constant of an RL circuit. The time constant is the ratio of inductance to resistance. It shows how quickly the circuit responds to a change in the input signal.

The current expression also lets us find the voltage across the resistor. It also lets us calculate the power dissipated in the resistor. Power is the rate at which energy is lost as heat. To find the total energy absorbed by the resistor, the power is integrated over time.

As time approaches infinity, the energy absorbed by the resistor approaches the initial energy stored in the inductor. This means the inductor’s energy is gradually transferred to the resistor until it is depleted. Understanding this transient response helps with circuit analysis. It is also useful in power electronics and communication systems, where inductors are used to filter or shape signals.

RL Circuit Decay After Source Removal

first-order circuits

First-Order Circuits in Flashing Lamps

First-order circuits use a resistor and one energy storage element, either a capacitor or an inductor. They are common in electronic systems and are described by a first-order differential equation that links the input and output signals. One important example is the RC circuit, which uses a resistor and a capacitor. In a relaxation oscillator such as a neon lamp circuit, the capacitor starts charging when voltage is applied. At first, the lamp behaves like an open circuit. When the capacitor...

rc circuit without source

RC Capacitor Discharge After Power Loss

An RC circuit discharges after the DC source is removed. If the capacitor was fully charged first, its initial voltage, V0, provides the energy that drives the source-free circuit. Kirchhoff’s current law is applied at the top node of the circuit. The current terms for the resistor and capacitor are then substituted, which leads to a first-order differential equation. Rearranging, integrating, and taking the exponential gives the natural response of the circuit. The integration constant in...

rc circuit with source

RC Circuit Charging After a DC Step

An RC circuit with a DC source shows how a capacitor charges after a sudden voltage step. The applied source is treated as a unit step function, and the capacitor voltage is the step response of the circuit. This response describes how the circuit reacts right after the input changes. A capacitor cannot change its voltage instantly. So, immediately after the switch closes at t=0, the capacitor voltage stays at its initial value. Kirchhoff’s current law is then applied at that moment and...

rl circuit without source

An RL circuit begins to decay after the DC source is removed. At that moment, the circuit becomes source-free. If the inductor has an initial current, I0, it also stores initial energy. That stored energy drives the natural response of the circuit. Kirchhoff’s voltage law is applied around the loop. The inductor voltage and resistor voltage are substituted into the equation. This gives a first-order differential equation for the current. Rearranging the terms produces a logarithmic form, which...

rl circuit with source

RL Step Response Under a DC Source

An RL circuit connected to a DC source has a step response that changes over time. The response has two parts: the transient response and the steady-state response. The transient response is the short-lived reaction that happens right after the source is applied. During the transient phase, the current changes exponentially. If the circuit starts with current in the inductor, that current decays toward zero as time goes on. At this stage, the inductor acts like a short circuit, so the source...

design example: frog muscle response

RL Circuit and Frog Leg Current Response

An RL circuit is used to model the frog leg’s response to electrical stimulation. In this setup, the student studies how current changes in a resistor-inductor circuit can trigger muscle contraction. The circuit provides a way to control and measure the electrical impulses involved in the experiment. When the switch is closed, the frog’s leg shows a brief contraction. At steady state, the inductor acts like a short circuit. That lets current bypass the resistor and produces a mild, short...

second-order circuits

RLC Damping and Resonant Frequency

Second-order circuits use two energy storage elements, such as a capacitor and an inductor, to shape how current and voltage change over time. These circuits include RLC circuits, along with RC and RL circuits that have two capacitors or two inductors. Their behavior is described by second-order differential equations that connect the input signal to the output signal. The input usually comes from a voltage source or a current source. The output is often the voltage across the capacitor, the...

series rlc circuit without source

Natural Response of a Source-Free RLC Circuit

A source-free RLC circuit is a series circuit with a resistor, inductor, and capacitor, but no external energy source. It begins with the energy already stored in the capacitor and inductor. That stored energy drives the circuit at first. The circuit is described by a second-order differential equation. This equation shows how the resistor, inductor, and capacitor interact over time. The resistor removes energy from the circuit, so the solution has an exponential form. When the exponential...

types of responses of series rlc circuits

types-of-responses-of-series-rlc-circuits

Damping in Series RLC Circuit Responses

A source-free series RLC circuit shows three response patterns based on damping. The circuit is described by a second-order differential equation. Its complete solution is made from two distinct solutions. Those solutions depend on the roots, which are written in terms of the damping factor and the resonant frequency. When the damping factor is greater than the resonant frequency, both roots are real and negative. This gives an overdamped response. The circuit output decays slowly over time. <br...

series rlc circuit with source

Forced Response in a Series RLC Circuit

A series RLC circuit with a DC source can model an automobile ignition system. The circuit shows how a battery can produce the high voltage needed for a spark. In this case, the input DC voltage acts like a forcing step function. Applying Kirchhoff's voltage law leads to a second-order differential equation. A second-order differential equation is an equation with a term for the second derivative. The form of this equation is very similar to the one used for a source-free RLC circuit, so the...

parallel rlc circuits

Parallel RLC Step Response in Surge Protectors

Parallel RLC circuits help explain how a surge protector works in a street lamp. The circuit model uses a DC input source that creates a step response when the switch is turned on. This setup shows how the lamp’s components can be protected from sudden voltage spikes. When the switch closes, Kirchhoff’s current law is applied to the parallel RLC circuit. That leads to a second-order differential equation. The solution has two parts: a transient response and a steady-state response. The...

second-order op amp circuits

Second-Order Op Amp Low-Pass Filters

Second-order op-amp low-pass filters remove unwanted high-frequency noise from audio signals. They are used in audio systems to refine sound quality. These filters are often built as voltage followers and have two nodes with storage elements. The circuit analysis follows the same basic method used for second-order RLC circuits. In practice, bulky inductors are usually avoided because of their size and weight. For that reason, the focus here is on RC second-order op-amp circuits, which are...

design example: underdamped parallel rlc circuit

design-example-underdamped-parallel-rlc-circuit

Oscillator Design with a Parallel RLC Circuit

A parallel RLC circuit can be designed to work as an oscillator with underdamped behavior. This example targets a damped natural frequency of 4 kHz and a damping factor of 4 radians per second. A fixed resistance of 200 Ω is used as the starting point for the design. The first step is to find the capacitance. The damping factor is the reciprocal of twice the product of resistance and capacitance. Using that relationship, the needed capacitance value can be calculated from the given resistance...

key terms and concepts

See how an RL circuit responds after the DC source is removed, with exponential current decay, time constant, resistor power, and energy loss as heat.

RL Circuit Decay After Source Removal | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

RL Circuit Decay After Source Removal

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