Electro Magnetic Induction And Alternating Currents Question 205
Question: A resistor ‘R’ and $ 2\mu F $ capacitor in series is connected through a switch to 200 V direct supply. Across the capacitor is a neon bulb that lights up at 120 V. Calculate the value of R to make the bulb light up 5 s after the switch has been closed, $ (log_{10}2.5=0.4) $
Options:
A) $ 1.7\times 10^{5}\Omega $
B) $ 2.7\times 10^{6}\Omega $
C) $ 3.3\times 10^{7}\Omega $
D) $ 1.3\times 10^{4}\Omega $
Show Answer
Answer:
Correct Answer: B
Solution:
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We have, $ V=V_{0}(1-{{e}^{-t/RC}}) $
$ \Rightarrow 120=200(1-{{e}^{-t/RC}})\Rightarrow t=RC $in $ (2.5)\Rightarrow R $
$ =2.71\times 10^{6}\Omega $
