Electric field due to point charge: E ∝ MCQ with Answer and Explanation

Explanation:
Acceleration due to gravity at height h: g' = gR²/(R+h)², where R is Earth's radius. Given h = R, so g' = gR²/(2R)² = gR²/4R² = g/4. This inverse square law dependence arises from Newton's law of gravitation. At depth, variation differs, but for height, this formula applies. Memory aid: Double the distance from center ⇒ gravity becomes one-fourth. This standard result is frequently tested in gravitation sections of competitive exams. Always verify whether height or depth is specified, as formulas differ significantly.

Explanation:
Heavy water (D₂O) slows neutrons, good moderator.

Explanation:
Rectifier (diode bridge) converts AC to DC. Inverter DC to AC. Transformer changes AC voltage level. Oscillator generates AC signal. Electronic devices often need DC.