Find the max induced EMF in the loop by the changing loop

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Homework Help Overview

The discussion revolves around calculating the maximum induced electromotive force (EMF) in a loop due to a changing current, as well as the induced EMF at a specific time. The subject area pertains to electromagnetism, specifically the principles of induction and the behavior of solenoids.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the formula for maximum induced EMF, questioning whether to include initial current in their calculations. There is discussion about dimensional analysis to verify the correctness of the equations being used.

Discussion Status

Some participants have provided insights into the dimensional analysis of the equations, while others have clarified the roles of various parameters in the context of the problem. There is an ongoing examination of the assumptions regarding the definitions of variables and their dimensions.

Contextual Notes

Participants note potential confusion regarding the definitions of certain variables, such as the time constant and the dimensions of specific terms in the equations. There is also mention of the relevance of textbook relationships in understanding the problem.

SpringWater
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Homework Statement


I have attached the two questions. the first has a diagram.

1. Find the MAX Induced EMF (in volts) in the loop by the changing current?

2. What is the magnitude of the EMF induced in the loop by the changing current at t=.8 (seconds) answer in Volts?


Homework Equations



All relevant equations are attached

The Attempt at a Solution



I believe I understand most of how to find the correct solution. However I am having trouble with deciding what is E(max) (1st question)? I am assuming I include E(max)=(μ)*(n)*(N)*(A) but i am not sure if i include I(initial)?

Any help will be greatly appreciated.
 

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SpringWater said:

Homework Statement


I have attached the two questions. the first has a diagram.

1. Find the MAX Induced EMF (in volts) in the loop by the changing current?

2. What is the magnitude of the EMF induced in the loop by the changing current at t=.8 (seconds) answer in Volts?


Homework Equations



All relevant equations are attached

The Attempt at a Solution



I believe I understand most of how to find the correct solution. However I am having trouble with deciding what is E(max) (1st question)? I am assuming I include E(max)=(μ)*(n)*(N)*(A) but i am not sure if i include I(initial)?

If all else fails, revert to dimensional analysis!
Letting E = emf, would E = (μ)*(n)*(N)*(A) be dimensionally correct?
Would E = (μ)*(n)*(N)*(A)*(i) be correct?
How about E = (μ)*(n)*(N)*(A)*(i)* (alpha)?
Hint: one of them is, the others are not.

PS otherwise what you did was fine.
 
rude man said:
If all else fails, revert to dimensional analysis!
Letting E = emf, would E = (μ)*(n)*(N)*(A) be dimensionally correct?
Would E = (μ)*(n)*(N)*(A)*(i) be correct?
How about E = (μ)*(n)*(N)*(A)*(i)* (alpha)?
Hint: one of them is, the others are not.

PS otherwise what you did was fine.

Thank you for the reply, I greatly appreciate it!

so here is what i have. A Volt units can be changed into a lot of different units. so

μ=(N) / (Amp)^(2)

n=turns / (meter)

N= Turns

I(initial)=Amp

Area=(meter)^(2)

alpha is (1) / (seconds) so then..

(Newton)*(Turns)*(Turns)*(meter^(2))*(Amp)
(Amp)^(2)*(meter)*(second)

then finally (N)*(Turn(in))*(Turn(out))*(Meter) / (Amp)*(second)

i am not sure how to eliminate turns?
 
N is dimensionless. But watch out: n has dimensions of 1/L.

You slipped up somewhere. i needs to be in the numerator, obviously.

Make life easier for yourself: you know from your textbook that for a solenoid B = μ0*i*n and you should know emf = -N*d(phi)/dt = -N*A*dB/dt in this case. So emf must look like
emf = A*B*T-1 = A*μ0*i*n*T-1.

In other words, no need to break everything down into fundamental units.
 
rude man said:
N is dimensionless. But watch out: n has dimensions of 1/L.

You slipped up somewhere. i needs to be in the numerator, obviously.

Make life easier for yourself: you know from your textbook that for a solenoid B = μ0*i*n and you should know emf = -N*d(phi)/dt = -N*A*dB/dt in this case. So emf must look like
emf = A*B*T-1 = A*μ0*i*n*T-1.

In other words, no need to break everything down into fundamental units.

okay, I assumed that T=time constant tau or in my case alpha. the answer was correct. thank you for the help
 
SpringWater said:
okay, I assumed that T=time constant tau or in my case alpha. the answer was correct. thank you for the help

Alpha is not the tme constant. 1/alpha is. Alpha has units of T^(-1) as it must since you need a di/dt term in your emf.
 

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