EECS 40 Midterm 1 - Spring 2001
Professor Howe
1. Capacitor Charging/Discharging [17 points]
(a) [4 pts] What is the value of the current i (t = 0
+
) in Amperes? The switch moves up at t = 0
and down at t = 50 ps. (note that 1 ps = 10
-12
s).
(b) [4 pts] What is the charge q on the + plate of the 1 pF capacitor in pC at t = 50 ps?
(c) [4 pts] What is the value of the current i (t = 50
+
ps) in Amperes? If you couldn't solve part
(b), you can assume for this part that q(t = 50 ps) = 5 pC. Needless to say, this is not the correct
answer to part (b).
(d) [5 pts] Accurately sketch the waveform vc(t) for 0<t<100 ps on the graph below. The values
at t = 0 and 50 ps should be accurate. You can make the same assumption in part (c) if you were
unable to solve part (b).
