Reference Designer Calculators
RC Time Constant Questions
Here are some of the questions related to RC time constant that can be used for Academic and Engineering ApplicationsQuestion 1
Consider the following RC circuit used for Power ON reset generation. What is the time constant of this circuit.
Answer
Since R = 100k and C = 0.1uF, the RC time constant according to the calculator is given by
T = 0.01 seconds or 10 milliseconds
Question 2
In the above circuit what should be the value of R for a time constant of 500 millisecods Answer
It will be 5 Mega Ohms. Obviously it is not a good design value ( a 5 Mega Ohm, dirts and moisture on PCB can change its value) to achieve 500 milliseconds delay. We may want to use a 1 Mega Ohm resistor with a 0.47 uF Cap to acheive a time constant of 470 milliseconds.
Question 3
An RC circuit is given a step voltage of V at t = 0 seconds. What is the value of voltage at t = 2RC. Answer
According to the equation
$ v(t)= ( 1-e^{-\frac{t}{RC}}).V $
At t = 2RC, we get
$ v(t)= ( 1-e^{-2}}).V $