# Rate of Field Change for Induced Current of Loop

by tevatron1
Tags: emf, induced current, loop, magnetic flux
 P: 11 1. The problem statement, all variables and given/known data A single conducting loop of wire has an area of 8.0×10−2 m^2 and a resistance of 110 Ω. Perpendicular to the plane of the loop is a magnetic field of strength 0.37 T. At what rate (in T/s) must this field change if the induced current in the loop is to be 0.33 A? 2. Relevant equations Trying to solve for ΔB/Δt 3. The attempt at a solution We have a change in magnetic flux, but it seems to be due to ΔB rather than ΔA, so Δflux = ΔB*Acosθ (However since cos(90) = 0, I'm not sure if this will be correct). Using Faraday's Law |ε| = N|(Δflux/Δt)| Substituted Δflux = ΔB*A into Faraday's Law --> ε = N(ΔB*A/Δt) Substituted the equation for the induced EMF into I = |ε|/R and solved for ΔB/Δt ΔB/Δt = I*R/A (N=1 because the loop has 1 turn) 453.75 T/s = (.33A)*(110Ω)/(8.0*10^-2 m^2) asks for 2 significant digits -> 450 T/s = Final Answer I'm not sure where I'm going wrong... 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution
P: 259
 Quote by tevatron1 1. The problem statement, all variables and given/known data We have a change in magnetic flux, but it seems to be due to ΔB rather than ΔA, so Δflux = ΔB*Acosθ (However since cos(90) = 0, I'm not sure if this will be correct). [/b]
θ would not be 90 as Area vector and B make 0 angle
P: 11
 Quote by kushan θ would not be 90 as Area vector and B make 0 angle
Okay, then cos(0) = 1, which would prove that my assumption Δflux = ΔB*A*cos(0) = Δflux = ΔB*A

How does the rest of my thought process look?

P: 259

## Rate of Field Change for Induced Current of Loop

as as i know you are doing correctly ,
where are you stuck ?
P: 11
 Quote by kushan as as i know you are doing correctly , where are you stuck ?
Mastering Physics tells me this is the wrong answer, though it does not give any explanation as to why.
 P: 259 what is " mastering physics "
P: 11
 Quote by kushan what is " mastering physics "
It's the online website for our physics homework. When you enter your answer, you are told whether or not your answer is correct. You are given 5 attempts, during which the points you earn diminish.
 P: 259 Even I am in confusion as they have given magnitude of magnetic field (which means a constant field ) but asking find at what rate it would vary
P: 11
 Quote by kushan Even I am in confusion as they have given magnitude of magnetic field (which means a constant field ) but asking find at what rate it would vary
Yes, I noticed this as well. I purposely left that out of my equation as we are attempting to solve for ΔB/Δt. I assume it's the authors of the homework trying to trick us into thinking the value is necessary. Though I cannot see how it could be.
 P: 259 I am sorry as I fail to help you further with this problem
 P: 1,508 You know the resistance of the loop and you know the current so you should be able to find the induced emf
 P: 11 "I am sorry as I fail to help you further with this problem " Thanks, Kushan. I appreciate your help. I think there might be an issue with the website. It wouldn't be the first time. Technician: You might notice that is exactly what I attempted to do... No worries though.
 P: 11 As it turns out, the website wanted a different number of significant figures. Albeit, an incorrect number with the given information...
 P: 259 Thank god

 Related Discussions General Physics 0 Introductory Physics Homework 1 General Physics 2 Advanced Physics Homework 1 Introductory Physics Homework 4