Question

A fresh dry cell of 1.5 volt and two resistors of `10 k Omega` each are connected in series. An analog voltmeter measures a voltage of 0.5 volt across each of the resistor. A `100 mu F` capacitor is fully charged using the same source. The same voltmeter is now used to measure the voltage across It. The initial value of the current and the time in which the voltmeter reading falls to 0.5 volt are respectively.
A. `60 muA,11s`
B. `120 muA,15 s`
C. `150 muA,m15 s`
D. `150 muA,11s`

Answer 1

Correct Answer - D
From the given conditions, resistance of analong voltmeter `= 10 k Omega`
initial current `= (1.5)/(10)mA`
`= (1500)/(10)muA = 150 muA`
Using, `0.5 = 1.5 e^(-t//RC) = 1.5 e^(-t//10)`
`t = 11 sec`