Answer to Question 3

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(a) t = 470 10-6 F 150 103 W = 70.5 s

(b) The voltage has risen to one half, so we have 1 half-life.  t1/2 = 0.693 70.5 s = 48.9 s 49 s (2 s.f.)

(c) The voltage is 63 % (100 % - 37 %).  V = 0.63   12 = 7.6 V (2 s.f.)

(d) The time for the capacitor fully to charge is 5 RC.  t = 352.5 s 350 s (2 s.f.)