Download Ee3305_prerequisite_exam_sample_questions

1. A 1.2 μF capacitor is initially charged to 50V.
How much energy is stored in the capacitor?
What will be the voltage on the capacitor after it has been discharged by a 10 μA
current for two seconds?
2. Consider the circuit below. After the switch has been closed for a long time,
determine the value of the currents as referenced in the schematic.
R3 = R4 = R5 = 10kΩ, L1 = 1mH, C1 = 100μF.
TCLOSE = 0
1
R3
2
i2
i1
R4
is
C1
2
R5
L1
Vs= 10V
1
is = _________
i1 = __________
i2 = __________
2
3. The switch in the circuit below has been closed for a long time. At t=0 the switch
opens. I3 = 5mA, R4 = 10kΩ and C3 = 1.2μF. If the voltage on the capacitor at t=0
is 25V, develop an expression for the voltage across the capacitor V(t) for t>0. Show
your work.
5mA
Switch open @ t=0
1
I3
R4
10k
+
V(t)
-
V(t) = ____________________________
C3
1.2uF
4. For the circuit shown below, I(t) = 100 cos(103t + 15), R = 10Ω, L1 = 5mH, L2,
L3 = 10mH and C = 100μF
L1
1
2
2
I1
L2
R1
I(t)
2
1
L3
C1
1
What is the RMS value of I(t)?
IRMS = _______________
What is the phasor representation of the current source?
Is = __________________
What is the phasor current through R1 ?
IR1= ___________________
What is the phasor voltage across the capacitor Vc
Vc = __________________
5. Consider the circuit shown below. I(t) = 40 cos(100t) A
V1
C2
V2
500 uF
I2
I(t)
2
R2
40
R3
10
L4
0.2 H
1
Write a simplified node equation for the V1 node.
(_________________) V1 + (________________) V2 = ___________
Write a simplified node equation for the V2 node.
(___________) V1 + (_________) V2 = ___________
Solve for the phasor voltages(magnitude and phase) V1 = ____________
V2 = ____________
6. For the circuit below, load A consumes 5kW at a 80% leading power factor. Load
B consumes 10 kW at 90% lagging power factor. The voltage source provides
5kVRMS.
5KV (rms)
A
B
Draw the power triangle for Load A. Label the power angle and all sides with
magnitude and sign.
Load A
Draw the power triangle for Load B. Label the power angle and all sides with
magnitude and sign.
Load B
Draw the power triangle for the Source. Label the power angle and all sides with
Source
magnitude and sign.
7. The input signal Vin(t) =
1 1
1
1
 cos(1000t ) 
cos(3000t ) 
cos(5000t )
2 
3
5
is applied to the input of a system with a transfer function shown graphically below.
H(f)
Vin(t)
Vout(t)
|H(f)|
/_H(f)
2
0
-45
-90
1000
2000
3000
f (Hz)
1000
2000
3000
f (Hz)
Looking at the magnitude graph of H (f), what kind of ideal filter is represented?
|H(f)| represents an ideal _____________ filter.
Write a time domain expression for Vout(t)
Vout(t) = ____________________________________
8. Given the cascaded system shown below, assume that the loading effects of the
second filter have been accounted for and that all phasors have a common frequency.
H1(f)
Vin
H2(f)
Vout
If Vin = 15/_ 0 , H1(f) = 3/_-25 , and H2(f) = 10/_ +15, write an expression for the phasor
output of the cascaded system Vout
.
Vout = ____________________
Using the values of H1(f) = 3/_-25 , and H2(f) = 10/_ +15, what is the magnitude of
H1(f) and H2(f) in decibels?
| H1(f)|dB = __________dB
9. In the circuit below, R =
| H2(f)|dB = ___________dB
500
Ω and C= 2μF.
2
What is the transfer function? ________________________
At what frequency, in Hertz, will the amplitude of the output signal, Vout(t) =
fb = ___________Hz
R
Vin(cos wt)
Determine the phase angle for Vout at f = fb?
C
Vout
_________________
Vin
2