Final answer:
The magnitude of the electric field between two charged parallel plates can be calculated using the surface charge density and the permittivity of free space, with direction from positive to negative plate.
Step-by-step explanation:
The student has asked to find the magnitude of the electric field between two charged parallel plates. To calculate this, we can use the equation for the electric field in a uniformly charged plate setup, which is E = σ / (2ε0), where σ is the surface charge density, and ε0 is the permittivity of free space. Given that the plates have charges of -0.225 C and +0.225 C, and each plate has an area of 0.75 m2, we first find the surface charge density σ by dividing the charge by the area. Then, plugging this value into the equation gives us the electric field magnitude. The direction of the electric field is from the positively charged plate to the negatively charged plate.