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PRACTICE / RC transients

A capacitor that does not start empty

A 20 μF capacitor initially at +4 V is connected through a 15 kΩ resistor to an ideal +10 V source, with the same voltage polarity.

Find the capacitor voltage 0.30 s after switching.

Organize the givens & assumptions
  • C = 20 μF
  • R = 15 kΩ
  • Initial capacitor voltage: +4 V
  • Source voltage: +10 V
  • Elapsed time: 0.30 s

Ideal series RC circuit; constant source; the capacitor voltage is continuous at switching.

  1. A10 V10\ \mathrm V
  2. B10−6/e V10-6/e\ \mathrm V
  3. C10(1−1/e) V10(1-1/e)\ \mathrm V
  4. D4/e V4/e\ \mathrm V

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