Suppose again you have an RC circuit with R = 50Ω, C = 0.2F, hooked up to a battery with V = 5V. This time we will discharge the capacitor.

Is the time constant τ different when we discharge a capacitor?

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  • \$\begingroup\$ Welcome! Is this homework? What have you tried so far? \$\endgroup\$
    – winny
    May 26 at 13:58
  • 1
    \$\begingroup\$ What do you mean "this time we will discharge the capacitor"? In an RC filter, the cap is discharged when you unplug the input voltage. \$\endgroup\$
    – Lundin
    May 26 at 14:01
  • \$\begingroup\$ It can be the same or different. Operating a switch changes the circuit. So you need to edit the question with a schematic diagram. Use the circuit lab tool in the question editor. \$\endgroup\$
    – RussellH
    May 26 at 14:20
  • \$\begingroup\$ That's quite the enormous capacitor. \$\endgroup\$
    – Hearth
    May 26 at 14:49
  • 2
    \$\begingroup\$ I’m voting to close this question because it appears to be an academic assignment but does not show an attempted solution. \$\endgroup\$ May 26 at 14:50

1 Answer 1


τ is defined as R*C. So whether the capacitor is charging or discharging, this will remain constant.

The equations for a capacitor charging and discharging do differ, but this doesn't change the value of τ

  • \$\begingroup\$ Only true for a particular case. \$\endgroup\$
    – RussellH
    May 26 at 14:21
  • \$\begingroup\$ In the case of the OP's description, this answer fits. It mentions only a resistor, capacitor and battery. I'm assuming from the question it is a homework type one in which case any extra resistance like a switch will be discounted as the learning exercises like to work with "ideals". However, I can change the answer if it's best \$\endgroup\$
    – MCG
    May 26 at 14:28

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