12th Class Physics Sample Paper Physics Sample Paper-4

  • question_answer
    Shikha went to the market with her brotherly metro. While passing through a gateway for security check she heard a long beep, as it was a metal detector which beeped. She was curious and asked about understood the reason of beeping from her class teacher. Read the above passage and answer the following questions :
    (i) On which principle does a metal detector work? What causes production of a beep in this case?
    (ii) Can the voltage drop across the inductor or the capacitor in a series L-C-R circuit be greater than the applied voltage of the AC source? Justify your answer.
    (iii) Write one value displayed by Shikha.


    (i) A metal detector works on the principle of resonance in AC circuits. Whenever a person walks through the gate of a metal detector, the impedance of the circuit changes. It results in appreciable change in current in circuit which causes production of sound in the form of a beep.
    (ii) Yes, because
    \[V=\sqrt{V_{R}^{2}+{{({{V}_{C}}-{{V}_{L}})}^{2}}}\] As, \[{{V}_{C}}\] and \[{{V}_{L}}\] have opposite faces, \[{{V}_{C}}\] or \[{{V}_{L}}\] may be greater than V when \[{{V}_{C}}>V.\] (iii) Curious and understanding.

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