Capacitor in a Non-Uniform Field?

📌 CONCEPT: When a capacitor is placed in a non-uniform electric field, the capacitance value changes due to the varying electric field strength between the plates.

📐 RULE / FORMULA: The capacitance of a parallel plate capacitor is given by the formula C = ε0A/d, where ε0 is the permittivity of free space, A is the area of the plates, and d is the distance between them.

💡 WORKED EXAMPLE: Consider a parallel plate capacitor with plates of area A and distance d between them, placed in a non-uniform electric field. If one plate is taken out of the field, the electric field strength between the plates will decrease, resulting in a decrease in capacitance. The stored charge Q remains the same, but the potential difference V will increase to maintain the same charge, as given by the equation C = Q/V.

⚠️ COMMON MISTAKE: Students often forget that the stored charge Q remains constant, but the potential difference V and capacitance C change when a capacitor is placed in a non-uniform electric field.