Download 1 - Marine Institute

ELECTROTECHNOLOGY
ELTK1200
REVIEW #1 (J. Matchem)
1.
An ac voltage supplied to a resistor produces a current of:
If the average power delivered to the resistor is 50mW, determine:
a) Value of R (in 6). (10.06)
b) Frequency and period of voltage waveform. (50Hz, 20mS)
c) Instantaneous voltage and power equations.
(
,
)
d) Instantaneous voltage at 5.5mSec. (.9878V)
.
2.
A 120V, 60Hz source is connected to a 1006 resistor.
a) Sketch the circuit.
b) Write instantaneous equations for voltage and current.
(
,
)
c) Find voltage and current at 10mSec. (-99.9V, -999mA)
3.
For a voltage given by the equation: v = 100 sin(1000t) V, find:
a) VRMS, (70.7V)
b) Frequency of voltage, current and power waves, (159Hz, fp = 318Hz)
c) Period, and (6.28mS)
d) Two times at which the instantaneous voltage is +80V. (.927mS, 2.21mS)
(Note: Find 2 times, t1 before the peak and t2 after the peak)
4.
For the two a.c. voltage equations shown:
v1 = 50 sin (377t) V
v2 = 76 sin (377t + 45°) V
a) Sketch/label a phasor diagram to represent the two waveforms.
b) Write them using phasor notation.
c) Calculate the RMS resultant of the two voltages. (82.6VRMS)
5.
For the 2 voltage phasors given:
a) Write corresponding instan. equations.
(
,
)
b) Find the RMS value of the resultant. (70.8V)
c) Write the instan. equation of the resultant. (
ELTK1200
Marine Institute
)
Rev 2
131
6.
A series R-L circuit consists of a 5006 resistor and a 2H inductor connected to a
120V, 60Hz source. Draw the circuit and:
a) Calculate circuit impedance and current. (9056, 132.6mA)
b) Sketch & label the impedance triangle and the phasor diagram.
( = 56.5°, VR = 66.3V, VL = 100V)
7.
An instantaneous voltage of v = 140 sin(314t + 10°)V is applied to the purely
inductive circuit shown.
a) What is the total inductive reactance of
the circuit? (2056)
b) Calculate instantaneous value of current
at 7.5mSec. (558mA)
(Hint: Write the equation)
(
)
c) Sketch waveforms for v & i on the same graph.
8.
For the purely inductive circuit shown, use voltage as the reference to:
a) find total inductive reactance. (37.76)
b) calculate instantaneous values of voltage and current at a time of 20mSec.
(32.3V, -278mA,
,
)
c) sketch v and i waveforms on the same graph.
9.
For the circuit shown, complete the following:
a) Find circuit impedance and current, (5846, 206mA)
b) Calculate the phase angle, and (31.1°lagging)
c) Draw and label the phasor diagram and impedance triangle.
ELTK1200
Marine Institute
Rev 2
132