QJEEM20Pha444: JEE Main 2020 Physics - Class 12 JEEM20Pha444 Solution: An emf of 20 V is applied at time t = 0 to a circuit containing …

Question

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An emf of 20 V is applied at time t = 0 to a circuit containing in series 10 mH inductor and 5

Ω

resistor. The ratio of the currents at time t =

\infty

and at t = 40 s is close to : (Take e² = 7.389)

Accepted Answer

i = i₀(1 -

e^{- \frac{R t}{L}}

)

i_$\infty$ = i₀(1 -

e^{- \infty}

) = i₀

∴

\frac{i_{\infty}}{i_{40 s}}

=

\frac{i_{0}}{i_{0} (1 - e^{- \frac{5 \times 40}{10 \times 10^{- 3}}})}

=

\frac{1}{(1 - e^{- 2000})}

\approx

1

Then most appropriate option is 1.06

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