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Railways PYQCBT 1 2016

RRB NTPC · Question 5

One should use porcelain and not metal containers in a microwave oven because _______ A. Charge may accumulate on the metal surface and there is danger of getting a shock. B. Porcelain vessels are better conductors of heat and thus food gets cooked quickly. C. Porcelain vessels have a high melting point. D. Porcelain vessels are cheaper than the metal containers.

  1. A

  2. B

  3. C

  4. D

Show answer & explanation

Answer: (A) A

Explanation

Microwaves induce electric charges and currents in metal surfaces, which can build up and cause sparks (arcing) that damage the oven and are dangerous. Porcelain lets microwaves pass through to heat the food, so it is safe. The official key gives the charge-build-up reason.