Electrical Engineering - Capacitors - Discussion
Discussion Forum : Capacitors - General Questions (Q.No. 11)
11.
A 4.7 M
resistor is in series with a 0.015 
F capacitor. The combination is across a 12 V source. How long does it take the capacitor to fully charge?
resistor is in series with a 0.015 F capacitor. The combination is across a 12 V source. How long does it take the capacitor to fully charge?Discussion:
20 comments Page 1 of 2.
Fazl hamad said:
1 decade ago
Dear fellow,
Usually time taken by a rc series circuit is T(TAU) = RC, but after 5 times of this time taken constant value.
The voltage across capacitor charges or discharges completely and and circuit seeks a steady state. The time taken is called transient period.
Usually time taken by a rc series circuit is T(TAU) = RC, but after 5 times of this time taken constant value.
The voltage across capacitor charges or discharges completely and and circuit seeks a steady state. The time taken is called transient period.
Lalithanandigam said:
8 years ago
As we know v =v(1-epower(-t/rc)).
So let us take t=Rc then v=v*0.63.
If u take t=5rc then v=v*0.993..
So during t=5rc capacitor is fully charged..
If you want to find the voltage across the capacitor after time t =5rc then we can use v=12*5*r*c.
So let us take t=Rc then v=v*0.63.
If u take t=5rc then v=v*0.993..
So during t=5rc capacitor is fully charged..
If you want to find the voltage across the capacitor after time t =5rc then we can use v=12*5*r*c.
Kanwaljit singh said:
9 years ago
5RC, in formula 5 is include because capacitor takes 5 times more time to charge itself when it is in series with resistor than normal charging so that why we use 5 constant in the formula.
Murtadha said:
9 years ago
Q = C*V = 0.015*10^-6 *12 =1.8^-7 colmb.
I = V/R = ( 12 / 4.7*10^6) =2.55*10^-6 amper.
I = Q/t 2.55*10^-6 = 1.8*10^-6 /t.
t= 70.5 ms.
So I think the choice (D) correct not (b).
I = V/R = ( 12 / 4.7*10^6) =2.55*10^-6 amper.
I = Q/t 2.55*10^-6 = 1.8*10^-6 /t.
t= 70.5 ms.
So I think the choice (D) correct not (b).
Abhishek said:
8 years ago
@Murtadha
The time required to charge a capacitor to 100% is 5T. Where t=R*c. that u got. not multiply that T with 5 you will get the answer.
The time required to charge a capacitor to 100% is 5T. Where t=R*c. that u got. not multiply that T with 5 you will get the answer.
Saurabh Kr. Verma said:
8 years ago
If t=5rc then it means there is no effect of 12V on it?
Is it take same time across any voltage?
Please tell me that.
Is it take same time across any voltage?
Please tell me that.
Vijay desai said:
1 decade ago
The time constant is five time greater when the capacitor is said to be fully charged. t = 5rc.
Yashwanth said:
5 years ago
Time Constant of Capacitor = 5RC.
T = 5 * (4.7*10^-6)(0.015*10^-3).
T = 352.
T = 5 * (4.7*10^-6)(0.015*10^-3).
T = 352.
Muhammad Azam Farooq said:
1 decade ago
Yes because capacitor always charge in 5 time constant.
Vishu said:
9 years ago
4.7 X .015/12 = .005875 X 60 =.352 sec.
=> 352ms.
=> 352ms.
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