Inductor Energy Loss Calculation

In summary, the conversation discusses the use of an inductor in an electrical circuit and the calculation of accumulated flux after a certain period of time. The participants mention the need for an equation that relates current to time and the use of an equivalent circuit to represent the situation. They also discuss the formula for calculating the inductor's work and the concept of energy loss due to the magnetic field. The conversation concludes with the reminder to account for losses by including the inductor's resistance in the calculations.
  • #1
Tom_Greening
13
0
I was so happy with the assistance provide here by NascentOxygen! Great contributor!
I have another question:

Homework Statement


A 20V battery is connected to an inductor with 1000μH that has 1000 turns with a cross section area of 1cm^2 is connected for 0.3 Sec during where 20J energy are lost over that period.

Calculate how much flux has accumulated after 0.3 Sec?



Homework Equations



This is where I need help. What equation do I start using? I understand it will be an integration with respect to time, but I am not sure where to start

The Attempt at a Solution

 
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  • #2
You are needing an equation that relates current to time, for a circuit comprising the elements relevant to the problem. :wink:
 
  • #3
Yes, i figured that. But not sure where to start looking for that.
If possible could you post the equation i need to start using.

so far I understand the 1J = 1A per second. So 20J = 20A per second.
I'm having difficulty associating the Joules in there.
 
  • #4
you first need to represent the situation as an electrical circuit, an equivalent circuit. How will you draw it using all ideal electrical elements?
 
  • #5
NascentOxygen said:
you first need to represent the situation as an electrical circuit, an equivalent circuit. How will you draw it using all ideal electrical elements?

Drawing it would be a DC supply connected to an inductor via a switch. I've seen many diagrams. I've read there is a small amount of resistance, but I think I should ignore that.

I've seen the formula I = Vb/R * (1-e^-tR/L)
 
  • #6
Tom_Greening said:
Drawing it would be a DC supply connected to an inductor via a switch. I've seen many diagrams. I've read there is a small amount of resistance, but I think I should ignore that.
Sometimes it is appropriate to make approximations, or overlook non-idealities, yes. Which element in your equivalent circuit is going to account for the 20 J mentioned?

I've seen the formula I = Vb/R * (1-e^-tR/L)
Something like that could be useful.
 
  • #7
The inductor has a work measured in Joules = 1/2Li^2 but I just can't get my head around the time component.
The formula says that the amount of work capacity is capable of inductor, but doesn't allow to incorporate the current in time.
 
  • #8
Tom_Greening said:
The inductor has a work measured in Joules = 1/2Li^2 but I just can't get my head around the time component.
The formula says that the amount of work capacity is capable of inductor, but doesn't allow to incorporate the current in time.
Whatever the current happens to be, that determines the stored energy at that moment.

The inductor stores energy, to release it later. The details about the 20 J uses the word "lost".
 
  • #9
NascentOxygen said:
Whatever the current happens to be, that determines the stored energy at that moment.

The inductor stores energy, to release it later. The details about the 20 J uses the word "lost".

Thankyou for the reply, but I'm still lost myself. What do you mean by the very last sentence?

I understand the concept after reading up on inductors that the inductor stores energy where current rises steadily, but due the electromagnetic motive force the inductor is resisting that with an opposing force where increasing current increase in flux. When the supply is disconnected the magnetic field dissappears, discharging and causing energy in the opposite direction.
I've dug up so many formulas but I'm going around in circles with this trying to put it in terms of formula that defines time..
 
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  • #10
Inductance does tend to impede any change in its current, as you describe.

Inductance stores energy, later releasing it all back into the circuit. Inductance does not cause a loss of energy from the circuit.
 
  • #11
Is it lost as heat then?
 
  • #12
Tom_Greening said:
Is it lost as heat then?
Yes.
 
  • #13
I think I have to go back and read more...
I'm reading a book here... energy is lost to the magnetic field...
 
  • #14
So would that mean the 20J information is not needed for the overall part of calculations since it is converted to heat?
 
  • #15
Loss due to straying magnetic field lines is typically infinitesimally tiny here.
 
  • #16
Tom_Greening said:
So would that mean the 20J information is not needed for the overall part of calculations since it is converted to heat?
If electrical energy is continually being lost from the circuit, then the inductor will be storing less energy than it otherwise would be. So you can't ignore this energy loss. You'll have to account for it.
 
  • #17
NascentOxygen said:
If electrical energy is continually being lost from the circuit, then the inductor will be storing less energy than it otherwise would be. So you can't ignore this energy loss. You'll have to account for it.
You account for losses by including the inductor's resistance. You cannot pretend it is zero.
 

FAQ: Inductor Energy Loss Calculation

What is an inductor?

An inductor is an electronic component that stores energy in the form of a magnetic field. It consists of a coil of wire that creates a magnetic field when an electric current passes through it.

How do you calculate the time constant of an inductor?

The time constant of an inductor can be calculated using the formula: T = L/R, where T is the time constant in seconds, L is the inductance in henrys, and R is the resistance in ohms.

What is the relationship between inductance and time in an inductor?

The relationship between inductance and time in an inductor can be described by its time constant. The time constant represents the time it takes for the inductor to reach 63.2% of its maximum current flow or energy storage capacity.

How do you calculate the energy stored in an inductor?

The energy stored in an inductor can be calculated using the formula: W = 1/2 * L * I^2, where W is the energy in joules, L is the inductance in henrys, and I is the current in amperes.

What factors affect the time constant of an inductor?

The time constant of an inductor can be affected by its inductance value, resistance in the circuit, and the type of material used for the core. The time constant also depends on the initial and final values of current in the inductor.

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