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Two coaxial long solenoids each carry current I, but inoppositedirections.

The inner solenoid has radius 'a' and has 'n_{1}' turns per unit length.

The outer solenoid has radius 'b' and has 'n_{2}' turns per unit length.

Find the magnetic field [itex]\vec B[/itex] in three regions:

1] inside the inner solenoid

2] between them

3] outside both

My work:

I worked out the solution for these. Someone verify if my answers are correct.

General formula for magnetic field for a solenoid of 'n' turns is:

[tex]\vec B = \mu_0 nI \hat k[/tex]

1] For inner solenoid:

[tex]\vec B = \mu_0 I n_1 \hat k[/tex]

2]Between the solenoids:

[tex]\vec B = \mu_0 I n_1\hat k - \mu_0 I n_2\hat k[/tex]

[tex]\vec B = \mu_0 I \left(n_1 - n_2\right)\hat k[/tex]

3]Outside both:

[tex]\vec B = 0[/tex]

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# Homework Help: Coaxial solenoids

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