Which of the following is a non-contact force? MCQ with Answer and Explanation

Explanation:
Using Gauss's law, for an infinite sheet, electric field E = σ/(2ε₀), directed perpendicular to the sheet. This is uniform and independent of distance from the sheet. Option A is for field near conductor surface; C and D are incorrect. Memory aid: 'Infinite sheet: E = σ/(2ε₀); conductor surface: E = σ/ε₀'. This conceptual question tests electrostatics fundamentals, crucial for competitive exams. Always distinguish between conducting and non-conacting sheets, as field expressions differ due to charge distribution.

Explanation:
Solar cell (photovoltaic cell) generates electricity from light.

Explanation:
At resonance frequency ω₀ = 1/√(LC), inductive reactance X_L = ωL equals capacitive reactance X_C = 1/(ωC), so they cancel. Impedance Z = √[R² + (X_L - X_C)²] = R, which is minimum (since R is the only remaining component). Current is maximum at resonance. Memory tip: 'LCR resonance: Z_min = R, I_max, purely resistive'. This AC circuit concept is frequently tested in competitive exams. Always distinguish series resonance (Z min) from parallel resonance (Z max) behavior.