A long thin non-conducting cylindrical pipe of radius R carrying a uniform surface charge density σ is rotating about its axis with a constant angular speed ω . The energy density of the magnetic field inside the tube is

Options

A. `(mu_(0)sigma^(2)omega^(2)R^(4))/(2)`
B. `(mu_(0)sigma^(2)omega^(2)R^(2))/(2)`
C. `(mu_(0)sigma^(2)omega^(2)R^(2))/(4)`
D. `(mu_(0)sigma^(2)omega^(2)R^(4))/(4)`

Answer

B