Graphing current vs. time in an RL circut

In summary, the conversation discusses the behavior of an inductor in parallel with a resistor when a voltage source is connected. It is noted that the current in an inductor starts small and grows exponentially until it plateaus, while voltage starts large and decreases. The concept of back EMF and Lenz's law are mentioned as factors that affect the behavior of the inductor. The conversation also mentions the equation for voltage drop over an inductor and how it relates to the current. It is concluded that the rate of change of current in the inductor can be determined and will gradually increase over time.
  • #1
Sheve
5
0

Homework Statement



Graph I(1) and I(2) vs. time. See attachment for illustration.

Homework Equations



V = IR
Back EMF = -L * dI/dt

The Attempt at a Solution



I realize that an inductor is essentially the opposite of a capacitor when it comes to current and voltage: that is, the current starts small and grows with an exponential curve until it plateaus while voltage starts large and drops to nearly nothing. However, I'm not sure how to treat this in parallel with a resistor. Assuming an ideal inductor with no resistance, it should carry a lot of current at the start since the R(L) of the equation of the voltage drop over the inductor V(L) = I(L) * R(L) will be close to zero...but I know this can't be the case!
 

Attachments

  • Graph I1 and I2.doc
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  • #2
The current was zero before connecting the voltage source to the coil. You know Lenz's law: The back EMF induced in the coil opposes the change caused by switching on the the battery. The back EMF prevents any abrupt change, the current will grow gradually, not necessarily in an exponential way.

The voltage across the inductor is negative of the back emf:

U = L dI/dt

U is given and constant if it is an ideal voltage source. It does not matter whether you connect a resistor parallel with the coil or not. You can determine the rate of change of I through the coil. This current was zero before the voltage source was switched on. How does the current change with time?

ehild
 

1. What is an RL circuit?

An RL circuit is an electrical circuit that contains a resistor (R) and an inductor (L) connected in series. It is used to study the behavior of current and voltage in circuits with inductors, which are components that store energy in the form of a magnetic field.

2. Why is it important to graph current vs. time in an RL circuit?

Graphing current vs. time in an RL circuit allows us to visualize the behavior of the circuit and analyze its characteristics. This can help us understand how the current changes over time and how the inductor affects the flow of electricity in the circuit.

3. How do you create a graph of current vs. time in an RL circuit?

To create a graph of current vs. time in an RL circuit, you will need to measure the current at different points in time using a multimeter and plot these values on a graph. The resulting graph will show how the current changes over time in the circuit.

4. What factors affect the shape of a current vs. time graph in an RL circuit?

The shape of a current vs. time graph in an RL circuit is affected by factors such as the inductance of the inductor, the resistance of the resistor, and the initial current flowing through the circuit. These factors can affect the rate at which the current changes and the overall behavior of the circuit.

5. How can current vs. time graphs in an RL circuit be used in real-world applications?

Current vs. time graphs in RL circuits can be used in real-world applications such as in power grids, electric motors, and generators. These graphs can help engineers design more efficient and reliable circuits by understanding the behavior of current and voltage in inductive circuits.

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