Which one of the following statements is correct regarding the magneti

Which one of the following statements is correct regarding the magnetic field inside a current carrying solenoid?

[amp_mcq option1=”The magnetic field inside the solenoid is zero” option2=”The magnetic field inside the solenoid is uniform at all the points” option3=”The magnetic field inside the solenoid increases as we move towards the ends” option4=”The magnetic field inside the solenoid decreases as we move towards the ends” correct=”option2″]

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UPSC Geoscientist – 2020

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The correct statement is that the magnetic field inside a current carrying solenoid is uniform at all points (for a sufficiently long solenoid). Option B is correct because, in the ideal case of an infinitely long solenoid, the magnetic field inside is perfectly uniform and parallel to the axis. For a real, long solenoid, this uniformity is a very good approximation over most of the interior volume, except near the ends.

For an ideal, infinitely long solenoid, the magnetic field inside is uniform and given by the formula B = μ₀ * n * I, where μ₀ is the permeability of free space, n is the number of turns per unit length, and I is the current. This formula shows the field is constant everywhere inside, independent of the position.

Outside a long solenoid, the magnetic field is nearly zero. Near the ends of a real solenoid, the magnetic field lines spread out, causing the field to become non-uniform and weaker than in the central region. However, in typical questions comparing the field at different points inside, the ideal case (uniform field) or the relative behavior (field strongest in the middle, weaker near ends) is considered. Option B represents the key characteristic of the internal field of a long solenoid.

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