Physics Help Forum inductive time constants

 Electricity and Magnetism Electricity and Magnetism Physics Help Forum

 Jul 10th 2010, 02:27 PM #1 Junior Member   Join Date: Jun 2010 Posts: 11 inductive time constants A resistance of 100,000 ohms is used to discharge a .47 uF capacitor that is charged to 1500V. a) How many time constants must elapse before the capacitor voltage falls to 10V? b)How much time must elapse? The only formula that I have for time constant is TC= L/R and I need to account for the fall in V but I'm don't know the formulas and steps to figure this one out.
 Jul 10th 2010, 07:42 PM #2 Senior Member   Join Date: Apr 2008 Location: HK Posts: 886 There is two more formula that you should remember. V=V0 * e^(-t/CR) and time constant= CR if i remember it correctly V is the potential difference of capacitor at an instant V0 is the initial potential difference of charged capacitor t is the time elapsed CR is the time constant for a circuit with a capacitor and a resistor __________________ Good results were achieved and the new task is to become a good doctor.

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