The discussion centers on the application of the Biot-Savart Law to a quarter loop example and the calculation of the magnetic field produced by a short coil with multiple loops. Participants clarify that the formula B*L = N*(μ)*I, which is typically used for infinitely long solenoids, must be adjusted for short coils, leading to the use of 2R instead of L. The magnetic field at the center of the coil is derived from the sum of the fields produced by individual loops, emphasizing the importance of understanding the geometry of the coil in calculations.
PREREQUISITESStudents of physics, electrical engineers, and anyone interested in electromagnetism and magnetic field calculations will benefit from this discussion.
kasse said:I also have a problem with this task:
http://www.badongo.com/pic/3641364
In a) I'm asked to show that the expression for B in P is correct, which I have made.
In b) the loop is replaced by a short coil with N loops. The direction of the current is the same. I'm asked to find
- the magnetic field in the center of the coil, and
- in what distance along the y-axis from the center of the coil is the B field reduced to 1/3 of it's maximal.
I use this formula to find the magnetic field in the center: B*L = N*(mju)*I --> B = N*(mju)*I/L
The answer is the same as in my book, except that L is replaced with 2R. Why is this? If the coil is short, it's length should definitely not be 2L!
alphysicist said:Hi kasse,
Here you want to think of the coils as being so short that the coils are effectively on top of one another. You can find the field of one loop at its center by using the result from part a; what is the value of y at the center of the loop? Then the magnetic field of N loops would just add together. Do you get the result?