Guess why Cylindrical Shell wants To contract it's surface?

Electricity and Magnetism Level 4

A very long thin cylindrical shell of radius $R$ carries uniform ucrrent $I_0$ along its length. Calculate the pressure on the wall of the cylindrical shell due to the magnetic force.

Details and Assumptions:

$I_0 = \sqrt{\pi} \times 10 \text{ Ampere}$ .
$R = 1\text{ mm}$ .
$\pi = 3.14$ .

Guess why Cylindrical Shell wants To contract it's surface?

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