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Unformatted text preview: RC time constant is = RC 8.4.2 Discharging a Capacitor If we move the switch in gure 25 to position b and repeat our analysis, we nd R dq dt + q C = 0 The solution to this homogeneous linear dierential equation is q = q e-t RC i =- q RC e-t RC So, we see that discharging a capacitor also has an exponential time dependence with the same characteristic time constant. 8.5 Problems Problem 27.33 In gure 26 the ideal batteries have emfs E 1 = 5 V and E 2 = 12 V , the resistances are each 2, and the potential is dened to be zero at the grounded point of the circuit. What are potentials (a) V 1 and (b) V 2 at the indicated points? The rst step in this problem is to simplify the two resistors in the upper right corner of the circuit. Since they are in parallel their equivalent resistance is P 1 = 1 1 R + 1 R = R 2 31...
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- Spring '08