ECE 220 Practice Exams

PART I

Tank ckt is tuned to 790kHz (KNST)

Natural response current of series RLC ckt starts at 0, ends (at t=inf)
at 0, and between these times exhibits decaying oscillations. The first
peak is positive since the cap begins to discharge and pushes current in
the direction shown. Answer (c)

Roots of an overdamped RLC ckt are negative and real

Uncharged cap passes current Is when a step current Is is applied.

Form of v(t) for RC ckt with 1V and 3V source is (d), which starts at 1V
and charges up to 2V.

RC ckt reaches steady-state after 5tau: 3.52s

PART II

v(0+) in RL ckt is -30V

RL ckt with make-before-break switch: Current = 5 + 13exp(-2000t) mA

Parallel RLC ckt is UNDERdamped

Pulse-excitation question. Answer is -1.11V

AC ckt. R=25ohms. (Cap and coil have equal and opposite impedances:
+j250 and -j250.)

Series RLC current = (4/3)[4.exp(-t)-exp(-4t)]