Induced current and force on circular loop in varying magnetic field

  • Thread starter Thread starter songoku
  • Start date Start date
AI Thread Summary
The discussion centers on the behavior of induced current and force in a circular loop within a varying magnetic field. It is asserted that the direction of the induced current remains anticlockwise, opposing the change in the magnetic field as per Lenz's law. However, a clarification is made that the induced current opposes the change in the magnetic field, not the field itself. Additionally, it is concluded that the net force on the loop is zero due to symmetry, as equal and opposite forces cancel each other out. Overall, the answers provided are deemed correct, with some corrections on the explanations regarding Lenz's law.
songoku
Messages
2,488
Reaction score
393
Homework Statement
A circular loop of radius r and resistance R is placed in magnetic field given by ##B(r,t)=B_o\left(1-\frac{r}{R_o}\right)e^{kt}## where ##B_o, ~k ~\text{and} ~R_o## are positive constant and ##r\leq R_o##
a) Describe qualitatively how the direction of the induced current changes
b) Find the net force experienced by the loop
Relevant Equations
##F=\int I d\vec l \times \vec B##

Faraday and Lenz Law
a) I don't think the direction of the induced current will change. Based on Lenz law, the circular loop will produce current that will oppose the varying magnetic field. Let's assume the direction of the varying magnetic field is into the page and the plane of the circular loop is perpendicular to the magnetic field so the direction of the induced current will be anticlockwise and will stay anticlockwise.

b) I think the net force will be zero due to symmetry since the opposite part of the wire will experience equal force but in opposite direction so they will cancel out

Are my answers correct? Thanks
 
Physics news on Phys.org
Is there any information about the direction of the magnetic field?
How is the loop oriented in the magnetic field?
Where is the center of the loop located in the magnetic field?
Was a diagram provided with this problem?
 
TSny said:
Is there any information about the direction of the magnetic field?
How is the loop oriented in the magnetic field?
Where is the center of the loop located in the magnetic field?
Was a diagram provided with this problem?
There is no diagram and no information about all of these. The question in ##1 is all of it.

I assume it will be like this:
1743467519382.png
 
songoku said:
a) I don't think the direction of the induced current will change. Based on Lenz law, the circular loop will produce current that will oppose the varying magnetic field. Let's assume the direction of the varying magnetic field is into the page and the plane of the circular loop is perpendicular to the magnetic field so the direction of the induced current will be anticlockwise and will stay anticlockwise.
The answer is correct, but the explanation is wrong. Your statement that the induced current generates a magnetic field which opposes the initial magnetic field is not correct. Lenz’s law states that the induced current generates a magnetic field which opposes the change of the initial magnetic field.

songoku said:
b) I think the net force will be zero due to symmetry since the opposite part of the wire will experience equal force but in opposite direction so they will cancel out
The answer is correct and the explanation is correct.
 
Thank you very much TSny and Gavran
 
  • Like
Likes Gavran and TSny
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Trying to understand the logic behind adding vectors with an angle between them'
My initial calculation was to subtract V1 from V2 to show that from the perspective of the second aircraft the first one is -300km/h. So i checked with ChatGPT and it said I cant just subtract them because I have an angle between them. So I dont understand the reasoning of it. Like why should a velocity be dependent on an angle? I was thinking about how it would look like if the planes where parallel to each other, and then how it look like if one is turning away and I dont see it. Since...
Back
Top