Determine the maximum magnetic flux through an inductor

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Homework Help Overview

The problem involves determining the maximum magnetic flux through an inductor connected to a standard outlet, with given voltage and frequency values. The context is within the subject area of electromagnetism, specifically focusing on inductance and magnetic flux.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to relate voltage and current to magnetic flux using formulas, but expresses confusion regarding the number of turns in the inductor. Other participants discuss the relationship between inductance and magnetic flux, questioning the assumptions made in the problem statement.

Discussion Status

Participants are exploring different interpretations of the problem, particularly regarding the definition of magnetic flux in relation to the number of turns in the inductor. Some guidance has been provided, but there is no explicit consensus on the interpretation of the question.

Contextual Notes

There is ambiguity in the problem regarding the number of turns in the inductor, which affects the calculation of magnetic flux. The original poster notes a lack of information about the value of N, which is crucial for solving the problem.

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I'm sure I'm going to kick myself when someone shows me the way, but there's a limit to how long I can stare at this question...

Determine the maximum magnetic flux through an inductor connected to a standard outlet (ΔVrms = 120 V., f = 60 Hz.)

That's all that's given.

I know that ΔVmax = 120*√2 and ω = 2Πf = 120Π and I think the magnetic flux will be at a maximum when the current is at a maximum, and
Imax = (ΔVmax) / (ω L) so

Imax = (120*√2) /(120ΠL)

Also, ΦB = I*L/N so I get

ΦB = (120*√2) /(120Π N)

but I have no idea what the value of N is for the inductor, & I can't see any way to get rid of that N. :frown:

(edited to correct 60 x 2 = 120, not 100 )
 
Last edited:
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Yeah, thanks Arcnets, that's basically the answer. My objection is that ΦB = IL if there's only one turn.

As you found in that Wolfram link, it comes from Faraday's
ε = -dΦB/dt
and
dΦB/dt ~ dI/dt (using ~ to mean proportional to)

From that, the inductance L is defined as the proportionality constant, so

dΦB/dt = L*dI/dt

and then, by integrating we get

ΦB = L* I

My objection is that in a coil with N turns, the inductance is
L = (NΦB)/I
and any inductor in a circuit is going to have more than 1 turn, so it seems to me that the question was, to say the least, ambiguous.

But, I asked the professor about it today and, yes, his answer was that the question "meant" the total flux through all the turns, in other words, they were looking for the value of N * ΦB, which of course is just
(120*√2) /(120Π) = .450 T*m2
 
Did you kick yourself?
 

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