Energy stored in an inductor of an LR circuit

In summary, to find the energy stored in the inductance of an LR circuit with R = 25 Ω, L = 5.4 mH, and EMF = 9.0 V, you need to find the current which is given by I = V/R. By a "steady" current, this means that dI/dt is equal to zero. Substituting the values, the standing current is equal to 0.36A. Using the equation Um = 1/2 LI^2, the energy stored in the inductance is calculated to be 0.35 mJ.
  • #1
OmegaFury
28
0

Homework Statement


An LR circuit has a resistance R = 25 Ω, an inductance L = 5.4 mH, and a battery of EMF = 9.0 V. How much energy is stored in the inductance of this circuit when a steady current is achieved?


Homework Equations


[itex]\epsilon[/itex]= -d[itex]\phi[/itex]m/dt=-L[itex]\frac{dI}{dt}[/itex]
Um=[itex]\frac{1}{2}[/itex]LI2
L=[itex]\phi[/itex]m/I


The Attempt at a Solution


According to the equations, to find the energy stored in the inductance of the circuit, I need to find current, but I don't know how. For the equation of emf, by a "steady" current, I suppose this means that dI/dt is equal to zero. I don't know how that helps, but it's as far as I got trying to understand this problem. Perhaps there is an equation that is necessary to solve this problem, but nothing comes to mind. Maybe... Ohm's law? But I doubt it as the potential difference across the circuit isn't known, and I don't think emf can be substituted for potential difference V even thought they have the same units (voltage).
 
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  • #2
You are on the right track!
The steady current is simply given by I = V/R
The inductance determines the RATE at which the current rises
 
  • #3
technician said:
You are on the right track!

Oh. So I was. Supposing emf can be substituted into I=V/R as V, then the standing current is equal to 9V/25 ohms= 0.36A. Um= 0.5(5.4 x 10-3H)(0.36A)2= 3.4992 x 10-4J= 0.35 x 10-3J= 0.35 mJ

That would be the correct answer. Thank you!
 

1. What is an inductor in an LR circuit?

An inductor is a passive electronic component that stores energy in the form of a magnetic field. It consists of a coil of wire that resists changes in current flow, causing it to store energy when current is flowing through it and release the energy when the current is interrupted.

2. How is energy stored in an inductor of an LR circuit?

Energy is stored in an inductor through the process of electromagnetic induction. When current flows through the coil, a magnetic field is created around it. This magnetic field stores energy and when the current is interrupted, the magnetic field collapses, releasing the stored energy.

3. What factors affect the amount of energy stored in an inductor?

The amount of energy stored in an inductor depends on its inductance, which is the measure of its ability to store energy, and the current flowing through it. Additionally, the number of turns in the coil and the material of the core can also affect the amount of energy stored.

4. How is energy released from an inductor in an LR circuit?

When the current in the circuit is interrupted, the magnetic field around the inductor collapses, inducing a voltage in the opposite direction. This induced voltage causes a current to flow in the opposite direction, releasing the stored energy from the inductor.

5. What is the relationship between inductance and energy stored in an inductor?

The amount of energy stored in an inductor is directly proportional to its inductance. This means that as the inductance of an inductor increases, so does the amount of energy it can store. Inductance is typically measured in henries (H) and energy is measured in joules (J).

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