Electromagnetic...

A spherical drop of mercury of radius R has a capacitance given by ‘C’. If two such drops combine to form a single larger drop, what is its capacitance?

A uniform volume charge density of 0.2 μ c/m³ is present throughout the spherical shell extending from r = 4 cm to r = 5 cm. If ρ_v = 0 elsewhere, then total charge present throughout the shell is ______ 

A parallel plate capacitor has plates of area A and separation d and is charged to a potential difference V. The charging battery is then disconnected, and the plates are pulled apart until their separation is 2d.

Given a parallel plate capacitor, dielectric filled, with area A = 100 cm², charge Q = 890 nC, and electric field E = 1.4 kV/mm.

For a given vector A = \(2\rho \cos \phi\) a_z in cylindrical coordinates, the value of \(\nabla \times A\) at (4,π, 0) would be