Which one of the following figures represents the radial electric field distribution  caused by a spherical cloud of electrons with a volume charge density,  for  (both  are positive and  is the radial distance) and  for  ?

Let  be the unit radial vector in the spherical co-ordinate system. For which of the following value(s) of , the divergence of the radial vector field  is independent of  ?

Consider two coupled circuits, having self-inductances  and , that carry nonzero currents  and , respectively. The mutual inductance between the circuits is  with unity coupling coefficient. The stored magnetic energy of the coupled circuits is minimum at which of the following value(s) of  ?

In the circuit shown,  and . It is supplied by a three phase  source with the phase sequence being R-Y-B. Assume the watt meters  and  to be ideal. The magnitude of the difference between the readings of  and  in watts is _______ (rounded off to 2 decimal places).

In the  coordinate system, three point-charges , and  are located in free space at , and , respectively. The value of  for the electric field to be zero at  is ________(rounded off to 1 decimal place).