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Physics XII Notes for Physics Notes

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Magnetic Field Along Axis Of Solenoid

A solenoid is a ling cylindrical coil having number of circular turns. Consider a solenoid having radius R consists of n number of turns per unit length. Let P be the point at a distance x̥ from the origin of the solenoid where we have to calculate the magnitude of the magnetic field. The current carrying element dx at a distance x from origin and a distance r from point P

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The magnetic field due to current carrying circular coil at any axis is:

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From figure we have,

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Now from above three equations, we get,

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Now total magnetic field can be obtained by integrating from Φ1 to Φ2, we get

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Hence this expression gives the magnetic field at point p of the solenoid of finite length.For infinite long solenoid

so,

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