AP Physics 2 / Unit 11: Electric Circuits
11.8 Resistor-Capacitor (RC) Circuits
Notes
- When charging, current starts high and drops; capacitor voltage rises toward the battery voltage.
- After a long time, a capacitor acts like an open circuit (no current through it).
- Time constant $\tau=RC$.
Practice
Right after closing a switch, an uncharged capacitor acts like:
No voltage across it yet.
After a long time, current through the capacitor branch is:
Fully charged.
$R=1{,}000$ Ω, $C=0.002$ F. $\tau=$
$RC$.
Ready for more? Take the Unit 11 test.