Register to reply

Energy stored in an inductor of an LR circuit

Share this thread:
OmegaFury
#1
Mar18-12, 04:02 PM
P: 28
1. The problem statement, all variables and given/known data
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?


2. Relevant 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


3. 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).
Phys.Org News Partner Science news on Phys.org
Hoverbike drone project for air transport takes off
Earlier Stone Age artifacts found in Northern Cape of South Africa
Study reveals new characteristics of complex oxide surfaces
technician
#2
Mar18-12, 04:21 PM
P: 1,506
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
OmegaFury
#3
Mar18-12, 04:43 PM
P: 28
Quote Quote by technician View Post
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!


Register to reply

Related Discussions
Energy stored in a RLC circuit Introductory Physics Homework 2
Stored Magnetic Energy - Inductor Circuit Introductory Physics Homework 8
The energy stored in an inductor Electrical Engineering 6
Energy stored in an inductor Introductory Physics Homework 7
How much of this energy is stored in the magnetic field of the inductor? Introductory Physics Homework 2