Electromagnetism - Find length of coil

AI Thread Summary
To calculate the length of an iron-free cylindrical coil with 9400 turns and an inductance of 68 mH, the formula L = N²μ₀μᵣA/l is used, where μ₀ is the magnetic field constant. The challenge arises from the unknown relative permeability (μᵣ) and cross-sectional area (A) of the coil. The thickness of the wire is given as 0.6 cm, which helps in determining the cross-sectional area for calculations. The discussion emphasizes the importance of unit consistency, noting that length should be in meters, area in square meters, and inductance in Henrys. Ultimately, the problem requires careful consideration of material properties and geometry to solve for the coil length.
Deathfish
Messages
80
Reaction score
0

Homework Statement


Calculate the length l of an an iron-free cylindrical coil if it has 9400 turns (N), a thickness of 0.6cm and an inductance L = 68 mH. Take magnetic field constant \muo = 4\pi x 10-7 Wb/Am

(a) l = 63mm
(b) l = 54mm
(c) l = 46mm
(d) l = 36mm

Homework Equations



L = N2 \muo \mur A / l

The Attempt at a Solution



0.068 = (9400)2 x ( 4\pi x 10-7) \mur A / l

how to calculate if \mur and A are not given??
 
Last edited:
Physics news on Phys.org
Given that the core is iron-free, what sort of material would you expect to find there? This material has a very nice relative permeability for calculations!

If you have a (circular cross section of a) piece of wire that is 0.6cm thick (diameter), what is the (cross sectional) Area of this wire?

*NB: Beware of units, as 'l' is in meters, 'A' is in meters squared and 'L' is in Henry's.
 
Last edited:
Thread 'Have I solved this structural engineering equation correctly?'

Thread 'Have I solved this structural engineering equation correctly?'

Hi all, I have a structural engineering book from 1979. I am trying to follow it as best as I can. I have come to a formula that calculates the rotations in radians at the rigid joint that requires an iterative procedure. This equation comes in the form of: $$ x_i = \frac {Q_ih_i + Q_{i+1}h_{i+1}}{4K} + \frac {C}{K}x_{i-1} + \frac {C}{K}x_{i+1} $$ Where: ## Q ## is the horizontal storey shear ## h ## is the storey height ## K = (6G_i + C_i + C_{i+1}) ## ## G = \frac {I_g}{h} ## ## C...
View full post »

Similar threads

Engineering Magnetic field strength of an electromagnet (coil wound around a bobbin)
Replies
17
Views
4K
Engineering Magnetic circuits with air coil question
Replies
2
Views
2K
Calculating B:I for Helmholtz coils
Replies
2
Views
4K
Engineering How to Calculate Reluctance and Estimate Force in a DC Electromagnetic Actuator
Replies
1
Views
3K
Electromagnetics: Non-Symetrical coil with external iron
Replies
4
Views
3K
Electromagnetism, current in coil
Replies
4
Views
4K
Low Level EMF and Helmholtz coil design
Replies
9
Views
3K
MATLAB Creating the Electric Octupole Tensor of a cubic electric octupole
Replies
1
Views
2K
Electromagnetic damping logarithmic decrement task
Replies
4
Views
2K
Calculate the inductance of a coil of wire
Replies
3
Views
3K

Hot Threads

Recent Insights

Back
Top