How long will it take to completely charge a 0.047 $\mu \mathrm { F }$ capacitor through a 1 $M \Omega$ resistor?
A) 0.029 s
B) 0.047 s
C) 0.235 s
D) 0.47 s

Question

How long will it take to completely charge a  0.047  $\mu \mathrm { F }$ capacitor through a 1 $M \Omega$ resistor?
A)  0.029 s
B)  0.047 s
C)  0.235 s
D)  0.47 s

Quizplus · Accepted Answer

The time constant, denoted by $	au$, is equal to the product of resistance and capacitance. 
$$	au = RC = (1\ M\Omega)(0.047\ \mu F) = 0.047\ ms$$
To find the time it takes to charge the capacitor to completion, we use the formula $t=5	au$, which gives us:
$$t = 5	au = 5(0.047\ ms) = 0.235\ ms$$
Converting to seconds, we get $0.235\ ms = 0.235\ s$, which is closest to option C.

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