A capacitor stores 10$\mu$C charge when connected across a battery. When the gap between the plates is filled with a dielectric, a charge of 20$\mu$C flows through the battery. The dielectric constant of the dielectric is

K = 3

In absence of dielectric

                        Q = CV = 10$\mu$C                                             . . . (1)

                        With dielectric

                              Q' = kCV = 30$\mu$C                                    . . . (2)

                        From (i) and (2) K = 3