# A closely wound solenoid of 800 turns and area of cross section $2.5 \times 10 ^{-4} m^2$ carries a current of 3.0 A. Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

In this case the magnetic field is generated along the axis / length of solenoid so it acts as a magnetic bar.

The magnetic moment is calculated as :-

$M\ =\ NIA$

or                                             $=\ 800\times 3\times 2.5\times 10^{-4}$

or                                              $=\ 0.6\ JT^{-1}$

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