Electric field increases as plate separation decreases at constant voltage

Steps:

• Voltage V across plates is constant from DC supply.
• Separation d decreases linearly with time t at constant speed: d = d₀ - vt.
• Electric field E = V/d, so E increases as 1/d.
• At midway point P, uniform field means E follows same variation.

Why D is correct:

• Graph D shows hyperbolic increase in E with t, matching E = V/(d₀ - vt) from capacitor field formula.

Why the others are wrong:

• A: Constant E implies unchanging d, but plates move closer.
• B: Linear E increase ignores inverse relation to d.
• C: Decreasing or non-increasing E contradicts rising field as d shrinks.

Final answer: D