A parallel-plate capacitor, with air in between the plates, has capacitance C. Now the space between the two plates of the capacitor is filled with a dielectric of dielectric constant 7. Then the value of the capacitance will become

The capacitance of a parallel-plate capacitor is determined by the geometry of the plates and the material between them. For an air-filled capacitor, the capacitance is given by C = ε₀A/d, where ε₀ is the permittivity of free space. When a dielectric material with a dielectric constant (K) is introduced to fill the entire space between the plates, the capacitance increases by a factor of K. This is because the dielectric reduces the electric field for a given charge, thereby reducing the potential difference and increasing the charge-storing capacity. In this specific case, the dielectric constant is 7. Therefore, the new capacitance C' is calculated as C' = K × C = 7C. While the provided options contain a typo (listing '1C' instead of '7C'), in standard physics problems of this type, the capacitance scales directly with the dielectric constant, resulting in a value seven times the original capacitance.