Q.

An infinitely long wire has uniform linear charge density λ=2 nC/m. The net flux through a Gaussian cube of side length 3 cm, if the wire passes through any two corners of the cube, that are maximally displaced from each other would be x Nm2C1, where x is: [Neglect any edge effects and use 14πε0=9×109 SI units]          [2025]

1 0.72 π  
2 4.44 π  
3 6.48 π  
4 2.16 π  

Ans.

(4)

ϕ=qenclosedε0

l=3a=3 cm

qenclosed=λl

 ϕ=λlε0

         =2×109×3×102×4π×9×109

         =2.16π