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A resistor 'R' and 2 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. ( ₁₀ 2.5=0.4 )

Options

  1. A1.7 10^5
  2. B2.7 10^6
  3. C3.3 10^7
  4. D1.3 10^4

Correct answer

B. 2.7 10^6

Step-by-step solution

V_c=E (1-e^ -t / R c )1-e^ -t / R c = 120 200 = 3 5 R= 5 1.84 10⁻⁶ =2.7 10^6

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