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Sunita and her friends visited an exhibition. The policeman asked them to pass through a metal detector. Sunita's friends were initially scared of it. Sunita, however, explained to them the purpose and working of the metal detector. Answer the following questions : (a) On what principle does a metal detector work? (b) Why does the detector emit sound when a person carrying any metallic object walks through it? (c) State any two qualities which Sunita displayed while explaining the purpose of walking through the detector. |
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Answer» (a) The metal detector works on the principle of resonance in ac circuit. (b) When Sunita's friend is passed through a metal detector, her friend in fact, passing through a coil of many turns. The coil is connected to a capacitor tuned so that the circuit is in resonance. When she walk through the metal in her pocket, the impedance of the circuit changes-resulting in significant change in current in the circuit. The change in current is detected and the electric circuitry causes a sound to be emitted as an alarm. |
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