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KVPY Sample Paper KVPY Stream-SX Model Paper-4

  • question_answer
    In the experiment of calibration of voltmeter, a standard cell of e. m .f. 1.1 volt is balanced against \[440 cm\] of potential wire. The potential difference across the ends of resistance is found to balance against 220 cm of the wire. The corresponding reading of voltmeter is 0.5 volt. The error in the reading of voltmeter will be:

    A) \[-0. 15 volt\]                 

    B) \[0.15 volt\]

    C) \[0.5 volt\]                    

    D) \[~-0.05\text{ }volt\]

    Correct Answer: D

    Solution :

    [d]
    In a voltmeter
    \[V\propto l\]  \[V=kl\]
    Now, it is given \[\operatorname{E}=1.1\] volt for \[{{l}_{1}}=440\operatorname{cm}\] and \[V=0.5volt\] for  \[{{l}_{2}}=220\operatorname{cm}\]    
    Let the error in reading of voltmeter be \[\Delta V\] then, \[1.1=400K\] and \[(0.5-\Delta V)=220K.\]
    \[\Rightarrow \]\[\frac{1.1}{440}=\frac{0.5-\Delta V}{220}\] \[\therefore \]\[\Delta V=-\,0.05\,volt.\]


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