When a dielectric slab fills only half the space between the plates of a parallel plate capacitor (connected to a batter
With a constant voltage V across the plates, the electric field E varies between regions. In the air region, E_{air = V/d, where d is the plate separation. In the dielectric region ( K > 1 ), polarization reduces the field: E_{dielectric = fracE_{airK = V/K d . Since K > 1, E_{dielectric < E_{air . The field differs because the dielectric polarizes, creating an opposing field that reduces the net field within it, while the air region experiences the full field.
Ref: NCERT Physics Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII, continuing as per NCERT advisory for 2026-27),Topic: Fundamental laws, definitions and applications as per latest NCERT. The section explains governing laws, formulas like μ₀ = 4π.