Digital Electronics - Multivibrators and 555 Timer - Discussion

Discussion :: Multivibrators and 555 Timer - General Questions (Q.No.4)

4. 

A 22-k resistor and a 0.02-F capacitor are connected in series to a 5-V source. How long will it take the capacitor to charge to 3.4 V?

[A]. 0.44 ms
[B]. 0.501 ms
[C]. 0.66 ms
[D]. 0.70 ms

Answer: Option B

Explanation:

No answer description available for this question.

Sujats said: (May 2, 2011)  
I want to know how to solve this problem or formula for it.

Sakshi said: (May 6, 2011)  
What is the formula to solve this problem.

Korsa Taressa said: (May 13, 2011)  
How the answer be 0.501 ms?

Shafeeq said: (Jul 2, 2011)  
Use this formula V=Vm(1-exp(-t/R*C))

Here all values are given and solve for t.

Arvind said: (Aug 6, 2011)  
What is other formula without calculator for exam?

Ambree said: (Oct 1, 2011)  
Wt is the formula to calculate with out calculator ?

Vikas Kaushik said: (Jan 10, 2012)  
V = Vo [ {exp(-t/RC) }- 1]
where
V = voltage across capacitor at any time t
Vo = supply voltage

K.K said: (May 8, 2013)  
The charging of capacitor is calculated.

T= ln(3) *RC.

Viendong194 said: (Feb 16, 2014)  
Yes. this is a monostable that made by IC555.
When Vc=2/3Vo , T=ln(3)*RC.

Mohit Sharma said: (Nov 4, 2014)  
V(c) = V(s)[1-e((-t)/RC)].
3.4 = 5[1-e((-t)/RC)].
3.4/5 = [1-e((-t)/RC)].
0.68 = 1-e((-t)/RC).
e((-t)/RC) = 0.32.

Taking natural log both sides, we have
-t/RC = -1.139.

t = 1.139 * 0.02u * 22K.
t = 0.501ms.

Aimal said: (Dec 17, 2014)  
t = RC*ln(Vc/Vs).

Uday Pratap Singh said: (Oct 20, 2016)  
Voltage across capacitor is,
Vc = V (1 - e^(-t/RC)).

From question Vc = 3.4V, V = 5V, RC = 0.44 x 10^-3.

Putting these values in above equation.
3.4 = 5 (1 - e^(-t/(0.44 * 10^(-3)))).

After solving this equation, t = 0.501 ms.

Harini said: (Feb 19, 2020)  
How this problem is solved. Are said a formula for this problem.

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