Haryana PMT Haryana PMT Solved Paper-2009

  • question_answer
    160W-60V lamp is connected at 60 V DC supply. The number of electrons passing through the lamp in 1 min is

    A)  \[{{10}^{19}}\]                                 

    B)  \[{{10}^{21}}\]

    C)  \[1.6\times {{10}^{19}}\]                            

    D)  \[1.4\times {{10}^{20}}\]

    Correct Answer: B

    Solution :

                    Power,   \[P=\frac{{{V}^{2}}}{R}\] \[R=\frac{{{V}^{2}}}{P}\]              \[=\frac{{{(60)}^{2}}}{160}=22.5\Omega \] Now, according to Ohms law                 \[V=IR\] \[\therefore \]  \[I=\frac{60}{22.5}\] \[\Rightarrow \]               \[I=2.6A\] Here,     \[t=60s\] As          \[I=\frac{ne}{t}\] \[\Rightarrow \]\[n=\frac{I\times t}{e}\]                 \[=\frac{2.6\times 60}{1.6\times {{10}^{-19}}}\]                 \[\approx {{10}^{21}}\] (The charge of electron \[e=1.6\times {{10}^{-19}}C\])


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