Advanced Qualification · A-001 Advanced theory · A-001-001-006
After two time constants, the capacitor in an RC circuit is charged to what percentage of the supply voltage?
- A 36.8%
- B 86.5%
- C 63.2%
- D 95%
Correct answer: B — 86.5%. From the official ISED question bank, verified word for word.
Why
After two time constants, the capacitor in an RC circuit reaches 86.5% of the supply voltage because it charges rapidly at first and then slows down, gaining about 63.2% of the remaining gap during each time interval. 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.