RC Circuit Time Constant
The time constant for an RC circuit is the amount of time it takes the capacitor in the circuit to either charge to 63.2% of it’s peak voltage, or to discharge to 36.8% of it’s peak voltage.
Once the capacitor in an RC circuit has discharged for one time constant, it is at 36.8% of its peak voltage. If it discharges for a second time constant, then it will be at 36.8% of 36.8% of it’s peak voltage: 13.5% of its peak voltage.
The formula for calculating the time constant of an RC circuit is:
Just multiply the resistance in the circuit by the capacitance.
Exam Questions
What is the term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the supply voltage?
A. An exponential rate of one
B. One time constant
C. One exponential period
D. A time factor of one
What is the term for the time it takes for a charged capacitor in an RC circuit to discharge to 36.8% of its initial value of stored charge?
A. One discharge period
B. An exponential discharge rate of one
C. A discharge factor of one
D. One time constant
The capacitor in an RC circuit is discharged to what percentage of the starting voltage after two time constants?
A. 86.5%
B. 63.2%
C. 36.8%
D. 13.5%