The resistance of a wire is R. If its length is doubled and area is halved, the new resistance is MCQ with Answer and Explanation

Explanation:
Inside a long solenoid, magnetic field is uniform (constant magnitude and direction), parallel to the axis, given by B = μ₀nI, where n is turns per unit length. Outside, field is nearly zero. This uniformity makes solenoids useful for creating controlled magnetic fields. Memory tip: 'Solenoid: uniform B inside like bar magnet'. This conceptual question tests knowledge of magnetic field configurations, crucial for electromagnetism in competitive exams. Always distinguish solenoid field (uniform inside) from straight wire field (circular, non-uniform).

Explanation:
Galvanisation: iron/steel coated with zinc to prevent corrosion. Zinc acts as sacrificial anode. Electroplating deposits metal layer using electricity. Alloying mixing metals. Annealing heat treatment.

Explanation:
For closed pipe, fundamental f = v/(4L) = 340/(4×0.16) = 340/0.64 ≈ 531 Hz, close to 512 Hz, slight difference due to end correction. So fundamental. Approx match, SSC type.