The instrument used to measure atmospheric humidity is MCQ with Answer and Explanation

Explanation:
g = GM/R², where M is mass of Earth, R radius, G universal constant. It does not depend on mass of falling object (Galileo's experiment). Earth's rotation causes slight variation but surface g is primarily determined by M and R. So mass of Earth is factor.

Explanation:
Magnetic field lines represent direction of force on an isolated north pole. They emerge from north and enter south. They never cross. Tangent gives field direction. Compass aligns along these lines.

Explanation:
Carnot efficiency η = 1 - T₂/T₁, where T₁ is source temperature, T₂ sink temperature (in Kelvin). Here T₁=400 K, T₂=300 K, so η = 1 - 300/400 = 1 - 0.75 = 0.25 = 25%. This maximum possible efficiency for given temperatures is a fundamental thermodynamics result. Memory tip: 'η_Carnot = 1 - T_cold/T_hot'. Competitive exams frequently test this formula with varying temperatures. Always use absolute temperatures (Kelvin); Celsius would yield incorrect efficiency. This problem assesses understanding of heat engine limitations.