The direction of induced current is given by MCQ with Answer and Explanation

Explanation:
T = 2π√(R/g) ≈ 5076 s ≈ 84.6 min for r ≈ Earth radius. Standard result. Memory aid: 'Low orbit: ~84 min; geostationary: 24 hours'. Orbital mechanics fact frequently tested in competitive exams.

Explanation:
Emission requires photon energy hν ≥ work function φ ⇒ ν ≥ ν₀. Intensity affects electron count, not emission possibility. Memory aid: 'Photoelectric: frequency threshold (quantum); intensity affects current'. Quantum physics concept frequently tested in competitive exams.

Explanation:
Carnot efficiency η = 1 - T₂/T₁, depending solely on absolute temperatures of heat source (T₁) and sink (T₂). It is independent of working substance, engine size, or other details. This universality makes Carnot cycle the theoretical maximum efficiency benchmark. Memory tip: 'Carnot efficiency: only T_hot and T_cold matter; real engines have lower efficiency'. This thermodynamics concept is frequently tested in competitive exams. Always recall that Carnot efficiency is an ideal limit; real engines have additional losses reducing efficiency below this value.