QJEEM11Ph295f: JEE Main 2011 Physics - Class 12 JEEM11Ph295f Solution: A resistor ′ R ′ and 2 μ F capacitor in series is connected…

Question

Verified Solution • 2025–26 Session moderate

A resistor

^{'} R^{'}

and

2 μ 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)

Accepted Answer

We have,

V = V_{0} (1 - e^{- t / R C})

\Rightarrow 120 - 200 (1 - e^{- t / R C})

\Rightarrow t = R C i n (2.5)

\Rightarrow R = 2.71 \times 10^{6} Ω

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