JEE Main & Advanced Physics Electro Magnetic Induction Question Bank Critical Thinking

  • question_answer
    An e.m.f. of 15 volt is applied in a circuit containing 5 henry inductance and 10 ohm resistance. The ratio of the currents at time \[t=\infty \] and at t = 1 second is       [MP PMT 1994]

    A)            \[\frac{{{e}^{1/2}}}{{{e}^{1/2}}-1}\]                              

    B)            \[\frac{{{e}^{2}}}{{{e}^{2}}-1}\]

    C)            \[1-{{e}^{-1}}\]                   

    D)            \[{{e}^{-1}}\]

    Correct Answer: B

    Solution :

                       \[i={{i}_{0}}(1-{{e}^{-Rt/L}})\] \[{{i}_{0}}=\frac{E}{R}\](Steady current)          when \[t=\infty \]                    \[{{i}_{\infty }}=\frac{E}{R}(1-{{e}^{-\infty }})=\frac{5}{10}=1.5\]            \[{{i}_{1}}=1.5(1-{{e}^{-R/L}})=1.5(1-{{e}^{-2}})\]Þ\[\frac{{{i}_{\infty }}}{{{i}_{1}}}=\frac{1}{1-{{e}^{-2}}}=\frac{{{e}^{2}}}{{{e}^{2}}-1}\]


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