A 10 µF capacitor is fully charged across a 12-volt battery. The capacitor is then disconnected from the battery and connected across an initially uncharged capacitor, C. The voltage across each capacitor is now 3 volts. What is the unknown capacitance C (in µF)?
Physics · Capacitor
JEE Advanced

Question

A 10 µF capacitor is fully charged across a 12-volt battery. The capacitor is then disconnected from the battery and connected across an initially uncharged capacitor, C. The voltage across each capacitor is now 3 volts. What is the unknown capacitance C (in µF)?

Physics · Capacitor

G1 Physics · Accepted Answer

Use the RC relation q = CE(1−e^(−t/τ)) or q = q₀e^(−t/τ), with τ = R(th)C. Substituting the given values gives 30.