ELECTRICITY FOR TRADES (LOOSELEAF)
3rd Edition
ISBN: 9781260437454
Author: Petruzella
Publisher: MCG
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Chapter 4.2, Problem 7RQ
To determine
State whether it is more expensive to operate a 1000-W dryer for 5 minutes or a 40-W lamp for 1 hour and provide a reason for this.
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Find Laplace transform and the corresponding ROC for
x(t) = e−3sin(2t) u(t)dt
Three similar coils, connected in star, take a total
power of 1.5 kW, at a power factor of 0.2, from a
three-phase, 400 V, 50 Hz supply. Calculate: (a) the
resistance and inductance of each coil; (b) the line
currents if one of the coils is short-circuited.
(a) Three 20 µF capacitors are star-connected across
a 400 V, 50 Hz, three-phase, three-wire supply.
Calculate the current in each line. (b) If one of the
capacitors is short-circuited, calculate the line cur
rents. (c) If one of the capacitors is open-circuited,
calculate: the line currents and the p.d. across each
of the other two capacitors.
ANS:
1.525 A; 2.64 A, 2.64 A, 4.57 A; 1.32 A, 1.32 A, 0;
210 V
Chapter 4 Solutions
ELECTRICITY FOR TRADES (LOOSELEAF)
Ch. 4.1 - What is the practical unit of electric charge?Ch. 4.1 - Prob. 2RQCh. 4.1 - Prob. 3RQCh. 4.1 - Explain what a current flow of 1 ampere can be...Ch. 4.1 - Account for the fact that electric current travels...Ch. 4.1 - Prob. 6RQCh. 4.1 - Prob. 7RQCh. 4.1 - Prob. 8RQCh. 4.1 - Prob. 9RQCh. 4.1 - Prob. 10RQ
Ch. 4.1 - Prob. 11RQCh. 4.1 - Prob. 12RQCh. 4.1 - What is the cause and effect of resistance?Ch. 4.1 - When using an ohmmeter to measure resistance, what...Ch. 4.1 - Convert the following data: a. 12,000 A to kA b....Ch. 4.1 - Prob. 16RQCh. 4.2 - Define electric power.Ch. 4.2 - What is the basic unit used to measure electric...Ch. 4.2 - A toaster draws 8 amperes when connected to a...Ch. 4.2 - Prob. 4RQCh. 4.2 - Prob. 5RQCh. 4.2 - Prob. 6RQCh. 4.2 - Prob. 7RQCh. 4.2 - Compare a closed and an open electric circuit.Ch. 4.2 - Prob. 9RQCh. 4.2 - What does Ohms law tell us about current flow in a...Ch. 4.2 - Ohms law is applied to a circuit using what three...Ch. 4.2 - Prob. 12RQCh. 4.2 - Prob. 13RQCh. 4.2 - Prob. 14RQCh. 4.2 - Prob. 15RQCh. 4.2 - Prob. 16RQCh. 4.2 - Prob. 17RQCh. 4.2 - Prob. 18RQ
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