# Help with home work question, RL circuit

• Engineering
• Quboid
In summary, the conversation revolves around finding the current in a circuit with a controlled current source. The speaker is having difficulty finding the forced response in the range 0 < t < 1.8 and is confused by the controlled current source. They have used Kirchhoff voltage law to find equations but are unsure of their accuracy. They are looking for a simpler way to calculate the current and will post a solution and diagram soon.
Quboid
vf= 4(u(t)-u(t-1.8))v

I have to find i(t), for the attached circuit. I already evaluated it for t<0. But i a having problems in the rage 0<t<1.8.

I am at the point where i have to find the forced response, so o let t tend to infinity
(t->infinity). And so the Inductor acts like a short circuit, the problem i have is find the current that passes where the inductor short circuits, I get confused by the controlled current sources.

I so far used kirchhoff voltage law to find three equations, but i am not sure i am correct, nor what to do with the dependent current source that finds itself in an equation.
Thanks for helping...

Quboid...

#### Attachments

• RL.001.jpg
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is there any simple way of calculating i1 in the circuit, that would make things a lot easier.

Ok, i am thinking i1=i-(4v/5ohms). Note i got the 4 volts( which is supplied by the independent voltage source) from the scalar function vf, when evaluated in the range 0<t<1.8.

I've never seen some of the circuit elements in your drawing. Who's reinventing electronics and why?

I think if you want any help, you're going to need to decode that stuff.

Sorry about that. I didn't use a circuit schematic program to draw the circuit. I actually labelled them. I was hoping that would be sufficient. I solved the question yesterday one hour before the class. I will post the solution and a proper diagram shortly.

## What is an RL circuit?

An RL circuit is an electrical circuit that contains a resistor (R) and an inductor (L). The resistor is a component that resists the flow of current, while the inductor is a component that stores energy in the form of a magnetic field.

## How does an RL circuit work?

In an RL circuit, the resistor and inductor are connected in series. When a voltage is applied to the circuit, the inductor initially resists the change in current and stores energy in its magnetic field. As the current continues to flow, the inductor's magnetic field begins to collapse, causing a change in current. This change in current creates a voltage drop across the resistor, resulting in a decrease in the overall current flow.

## What is the time constant in an RL circuit?

The time constant, denoted by the symbol τ, is a measure of the rate at which the current changes in an RL circuit. It is calculated by dividing the inductance (L) by the resistance (R). The time constant is important in determining the behavior of an RL circuit, such as how quickly the current reaches its steady-state value.

## How can I solve for the values in an RL circuit?

To solve for the values in an RL circuit, you can use various formulas such as Ohm's law and Kirchhoff's laws. These laws can help you calculate the voltage, current, and resistance in the circuit. You can also use simulation software or perform experiments to determine the values in an RL circuit.

## What are some real-life applications of RL circuits?

RL circuits have many practical applications in everyday life. They are used in electronic filters, such as in audio systems and communication devices, to block or pass certain frequencies. They are also used in power supplies, motors, and generators, where the inductor helps regulate the flow of current. Additionally, RL circuits are used in ignition systems in cars and in electronic dimmer switches to control the brightness of lights.

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