Final answer:
The energy stored between two square plates of a capacitor is calculated using the formula U = ½ CV^2, where the capacitance (C) depends on the plate area and separation. Without the voltage value, the exact energy cannot be determined; however, the capacitance can be found with the given dimensions.
Step-by-step explanation:
Energy Stored in an Electric Field
The energy stored by the electric field between two parallel plates can be calculated using the formula for the energy (U) stored in a capacitor: U = ½ CV^2, where C is the capacitance and V is the voltage across the plates. To find the capacitance, we use the formula C = ε0εrA/d, with ε0 being the vacuum permittivity, εr the relative permittivity of the dielectric (which is 1 for air), A the area of the plates, and d the separation distance between the plates. Given that the plates are 8.0 cm on a side and separated by a 1.3-mm air gap, we can calculate the energy stored in this system.
The area A = (8.0 cm x 10-2 m/cm)2 = 6.4 x 10-4 m2 and the distance d = 1.3 mm x 10-3 m/mm = 1.3 x 10-3 m. Substituting the values into the formula gives us the capacitance. Without the voltage value provided, we cannot calculate the exact energy value, but having found the capacitance, one would only need to apply the voltage to the formula for energy to get the final answer.