Question

The time constant for RC circuit with the values of R1 and C1 is 5ms. What will be the time constant for a new RC circuit with the values: R2=10R1 and C2 = 0.5C1.
a. 2.5ms
b. 15.5ms
c. 50ms
d. 25ms
e. 15ms

Answer 1

Answer:

d. 25 ms

Explanation:

• In a RC circuit we call time constant to the product of the resistance times the capacitance, which represents the time when the charge reaches to the 63% of the final value, as follows:

       $\tau_{1} = R_{1} *C_{1} = 5 ms (1)$

• If we have a new circuit with new values for R and C, the time constant will be defined in the same way, as follows:

       $\tau_{2} =10* R_{1} *0.5*C_{1} = 5*(R_{1}* C_{1}) = 5* \tau_{1} = 5* 5 ms = 25 ms (2)$