Magnetic force on sides of square solenoid

AI Thread Summary
The discussion centers on calculating the magnetic forces and torque on a square solenoid with a 5-turn coil carrying a current in a uniform magnetic field. The force on sides ab and cd was calculated to be 0.0021 N, with ab directed in the positive k direction and cd in the negative k direction, while sides bc and da experience no force. A key question raised was whether to consider the magnetic force generated by the solenoid itself in addition to the external magnetic field when calculating total force. The participant eventually resolved their confusion regarding the calculations. The thread highlights the complexities of analyzing forces in magnetic fields for coils and solenoids.
physicsnublet
Messages
2
Reaction score
0

Homework Statement


A square 5-turn coil with sides .03 m long and carrying 2 A of current is placed in a uniform magnetic field of .07 T, as shown.

What is the magnitude and direction of the force on each of the four sides?

What is the magnitude and direction of the torque \tau on the coil about its center, if any? Use the fact from mechanics that \tau = r x F due to a force F applied with lever arm r.

What is the magnetic moment \mu of this coil? What is the torque on the coil evaluated using the relation \tau = \mu x B?


Homework Equations


Force on a current-carrying wire
F=I\hat{l}x\vec{B}

Field of ideal solenoid
B=\mu_{0}NI\overline{l}

The Attempt at a Solution


I wasn't sure how to translate F=I\hat{l}x\vec{B} into a coil with 5 loops, so I just multiplied IN\hat{l}x\vec{B}=(2A)(5 loops)(.03m)(.07T)=.0021 N for sides ab and cd. By right hand rule, I said ab is in the +\hat{k} direction and cd is in the -\hat{k} direction. I said bc and da were parallel to B so there was no force on them.

My biggest question: When you calculate force of a coil in a uniform magnetic field, do you have to take into account the force that comes from the current itself?
The uniform magnetic field seems to be from an external source, so to find total force do I also have to use the solenoid to find field and force from that, then add that force to the uniform field's force?

Thanks very much for any help; I'm rather stumped by all this.
 

Attachments

  • lab5.jpg
    lab5.jpg
    9.4 KB · Views: 584
Physics news on Phys.org
Nevermind, I figured it out.
 
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 .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top