To demonstrate the large size of the henry unit, a physics professor wants to wind an air-filled solenoid with self-inductance of 1.0 HH on the outside of a 15 cmcm diameter plastic hollow tube using copper wire with a 0.93 mmmm diameter. The solenoid is to be tightly wound with each turn touching its neighbor (the wire has a thin insulating layer on its surface so the neighboring turns are not in electrical contact).

Required:
a. How long will the plastic tube need to be?
b. How many kilometers of copper wire will be required?
c. What will be the resistance of this solenoid?

Respuesta :

Answer:

Following are the solution to the given points:

Explanation:

For point a:

Following are the expression to the self- inductance and the solenoid:

[tex]L=\frac{\mu_0 N^2 A}{l}[/tex]

   [tex]=\frac{\mu_0 (\frac{l}{d})^2 (\pi r^2)}{l}\\\\=\frac{\mu_0 ( \pi(\frac{D}{2})^2)}{d^2}\\\\=\frac{Ld^2}{\mu_0( \pi (\frac{D}{2})^2)}\\\\=\frac{(1.0 \ H)(0.77 \times 10^{-3} \ m)^2}{ 4 \pi \times 10^{-7} \frac{H}{m} (\pi (\frac{13 \times 10^{-2} \ m }{2})^2)}\\\\=35.5 \ m[/tex]

For point b:

Calculting the length of the copper wire:

[tex]L'=N(\pi D)[/tex]

[tex]=\frac{l}{d}(\pi D)\\\\=\frac{35.5 m}{0.77 \times 10^{-3} m}\pi (13\times 10^{-2} m)\\\\=18829.2 \ m(\frac{1 km}{10^3 \ m})\\\\=18.8 \ km[/tex]

For point c:

The resistance of the solenoid is given by,

[tex]R=\frac{\rho L'}{A}[/tex]

   [tex]=\frac{\rho L'}{\pi r'^2}\\\\=\frac{\rho L'}{\pi (\frac{d}{2})^2}\\\\=\frac{(1.68\times 10^{-8} \Omega . m) (18829.2 \ m)}{\pi (\frac{0.77 \times 10^{-3} \ m}{2})^2}\\\\=6793 \ \Omega[/tex]