Advanced Qualification · A-001 Advanced theory · A-001-001-007
After two time constants, the capacitor in an RC circuit is discharged to what percentage of the starting voltage?
- A 63.2%
- B 13.5%
- C 36.8%
- D 86.5%
Correct answer: B — 13.5%. From the official ISED question bank, verified word for word.
Why
After two time constants, a capacitor in an RC circuit has lost about 86.5% of its starting voltage, leaving only 13.5% remaining. The full explanation — and one for every question — is in Pro.
Practise this section
Advanced theory: time constants, reactance, impedance, resonance, Q, and the mathematics behind tuned circuits.