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Fazza3_uae

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## Homework Statement

A 3 m long large coil with a radius of 15.7 cm and 130 turns surrounds a 7.2 m long solenoid with a radius of 5.7 cm and 4700 turns. The current in the solenoid changes as [tex] I=I_0 sin (2\pi f t) [/tex] where I

_{0}= 30 A and f=60 Hz.Inside solenoid has 4700 turns and outside coil has 130 turns. The equation for the emf is [tex] E= E_0 sin \omega*t [/tex] .There is also a resistor on the smaller coil that is 34 ohms. Find the maximum induced emf in the large coil. Answer in units of V.

http://img194.imageshack.us/img194/5624/87290481.jpg

## Homework Equations

Faraday's law od induction

[tex] emf = -N\frac{d\phi}{dt}[/tex]

Magnetic field of solenoid

[itex]\mu_0IN/L[/itex]

## The Attempt at a Solution

I will show my work done till now.If there is any mistake i made or step i forgot please tell me.

First i have to find the magnetic field of the inner solenoid.

Then i have to calculate the flux of the inner solenoid.

After that i have to use the magnetic field of inner solenoid to find the flux of outer solenoid.

Now i have to find the change in flux but the question here is , Do i have to subtract the inner from the outer or the opposite ?

Is is [tex]\phi[/tex]

_{Outer}- [tex]\phi[/tex]

_{Inner}?

Or [tex]\phi[/tex]

_{Inner}- [tex]\phi[/tex]

_{Outer}?

Now i know that i have to derive the flux change with respect to time but another question is here , shall i subtract the two fluxe first then derive the change or shall i derive them before subtraction ? ( I think that i will get the same answer whatever choice i select )

After i get the answer ( which i hope to get it very soon ) i will just multiply the whole thing i mean the time rate of change of that flux with the number of turns for the outer solenoid .

Please check my steps & tell me if i did something wrong.

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