NEET Physics Thermometry, Calorimetry & Thermal Expansion NEET PYQ-Thermometry, Calorimetry and Thermal Expansion

  • question_answer
    On a new scale of temperature (which is linear) and called the W scale, the freezing and boiling points of water are \[39{}^\circ W\] and respectively. What will be the temperature on the new scale, corresponding to a temperature of \[39{}^\circ W\] on the Celsius scale?                                                                   [AIPMPT (S) 2008]

    A)  \[78{}^\circ \,W\]        

    B)       \[117{}^\circ \,W\]

    C)  \[200{}^\circ \,W\]      

    D)       \[139{}^\circ \,W\]

    Correct Answer: B

    Solution :

    In general, whenever we are to go from any known scale to any unknown scale, then we follow the equation    
    (Temperature on known scale)
    \[\frac{-\text{(LFP}\,\text{for}\,\text{known}\,\text{scale)}}{{{\text{(UFP}-\text{LFP)}}_{\text{known}}}}\]
    (Temperature on unknown scale)
    \[\text{=}\frac{-\text{(LFP}\,\text{for}\,\,\text{unknown}\,\text{scale)}}{{{\text{(UFP}-\text{LFP)}}_{\text{known}}}}\]
    or         \[\frac{39-0}{100-0}=\frac{t-39}{239-39}\] or \[t={{117}^{o}}W\]
    Note:    LFP \[\to \]Lower fixed point
    UFP\[\to \] Upper fixed point
    Alternative:
    \[\begin{matrix}    \text{10}{{\text{0}}^{\text{o}}}\text{C}  \\    {}  \\    {{\text{0}}^{\text{o}}}\text{C}  \\ \end{matrix}\underline{\overline{\underset{\downarrow}{\overset{\uparrow }{\mathop{100}}}\,\text{division}\underset{\downarrow }{\overset{\uparrow }{\mathop{200}}}\,}}\,\begin{matrix}    \begin{align}   & \text{Now}\,\text{scale} \\  & \text{23}{{\text{9}}^{\text{o}}}\text{W} \\ \end{align}  \\    \text{divisions}  \\    \text{3}{{\text{9}}^{\text{o}}}\text{W}  \\ \end{matrix}\]
    \[\therefore \]      \[{{39}^{o}}C=39\times 2+39={{(78+39)}^{o}}W\]
    \[={{117}^{o}}W\]


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