ECE 2006 UMD Fall, 2006

Name:__________________________EXAM I: 100 Points, Show work for partial credit.

1a. Given I(t) in the graph below, find:

(7pts) The charge, q(t), for 2<t<4 seconds (6pts) Also, compute q(4 seconds)

Answers:q(t) = -1.25t2 +10t -10 + q(0) mC, 2 < t < 4 sec; q(4) = 10 mC + q(0)

1b. The charge delivered to the resistor shown below is described by the following equation: q(t) = -120 e-5t microcoulombs

(6pts) Calculate I(t).(6pts) Also, for the diagram shown, if V = 1.2 e-5t Volts, find the value of R, in Ohms using

your value for I(t).

Answers: I(t) = 600 e-5t microamperes; R = 2 k-ohm

Scott Norr Page 1 5/25/2023

ECE 2006 UMD Fall, 2006

2a. (15pts) In the diagram, find the value of R2, in terms of R1, that will satisfy Req = 2R1.

Answer: R2 = 2R1

2b. (10pts) Find a value for Ra in the diagram that makes Req = 10 Ohms

Answer: Any value, 0 <= Ra < ∞

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ECE 2006 UMD Fall, 2006

3. (25pts) Solve by any method for: Io: Vo:

Answers:Vo = 6.5 volts ; Io = -3.5 mA

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ECE 2006 UMD Fall, 2006

4. Solve for:(15pts) Vo, by any method

(10pts) The power supplied or absorbed by the source, V2.

Answers:

Vo = 7 volts; PV2 = -50 W

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ECE 2006 UMD Fall, 2006

Bonus 1: Apply Ideal Op Amp Assumptions to the amplifier circuit below. Find:a. An equation for Vo, in terms of the input voltage, Vs.b. If Vs = 2 volts, calculate Vo.c. For Vs = 2 volts, calculate Io. (If you’re unable to answer part b., you may assume a value for

Vo and proceed for full credit)

Answer: Vo = 40 - 11Vs volts; Vo = 15 volts (saturated); Io = 3.100 mA (3.1083 mA if you really know your stuff)

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ECE 2006 UMD Fall, 2006

Bonus 2: For the following steady-state DC circuit:

5 Pts – Find Ix10 Pts – Find Vx 5 Pts – Find V-thevenin between A and B 5 Pts – Find R-thevenin between A and B

Answers:

Ix = 2 amps; Vx = 30 volts; Vthev = 30 volts; Rthev = 15 ohms

Scott Norr Page 6 5/25/2023