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The charge flown through a resistance R in time t varies with time according to \mathrm{Q}=\mathrm{at}-\mathrm{bt}^2.
 The total heat produced in R by the time current becomes zero is :

Option: 1

\frac{a^3 R}{6 b}


Option: 2

\frac{a^3 R}{2 b}


Option: 3

\frac{a^3 R}{3 b}


Option: 4

\frac{a^3 R}{b}


Answers (1)

best_answer

\mathrm{Q}=\mathrm{at}-\mathrm{bt^{2 }}           \Rightarrow       \mathrm{i}=\frac{\mathrm{dQ}}{\mathrm{dt}}=\mathrm{a}-2 \mathrm{bt}

Current becomes zero at time   t=\frac{a}{2 b}

Total heat produced  =\int_{t-0}^{t-2 / 2 b} i^2 R d t=\int_0^{a / 2 b}(a-2 b t)^2 R d t=\frac{a^3 R}{6 b}

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Rishi

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