The human ear can hear sound in frequency range MCQ with Answer and Explanation

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:
At 0°C, speed ~ 331 m/s. At room temperature (20°C) ~ 343 m/s, often taken as 340. Increases with temperature v ∝ √T. For many problems 340 is used, but at 0°C it's 331. So option A.

Explanation:
ΔL = α L₀ ΔT => α = ΔL/(L₀ ΔT) = 0.0019/(1×100) = 1.9×10⁻⁵ /°C. Typical for brass. Unit is per °C. Always check ΔL/L per °C.