Page 17 - Schaum's Outline of Theory and Problems of Electric Circuits

[CHAP. 1
INTRODUCTION
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The ampere-hour rating is a measure of the energy the battery stores; consequently, the energy trans-
ferred for total discharge is the same whether it is transferred in 10 hours or 20 hours. Since power is the
rate of energy transfer, the power for a 10-hour discharge is twice that in a 20-hour discharge.

Supplementary Problems

1.8 Obtain the work and power associated with a force of 7:5 10 4 N acting over a distance of 2 meters in an
elapsed time of 14 seconds. Ans. 1.5 mJ, 0.107 mW

1.9 Obtain the work and power required to move a 5.0-kg mass up a frictionless plane inclined at an angle of 308
with the horizontal for a distance of 2.0 m along the plane in a time of 3.5 s. Ans. 49.0 J, 14.0 W

1.10 Work equal to 136.0 joules is expended in moving 8:5 10 18 electrons between two points in an electric
circuit. What potential difference does this establish between the two points? Ans. 100 V

1.11 A pulse of electricity measures 305 V, 0.15 A, and lasts 500 ms. What power and energy does this represent?
Ans. 45.75 W, 22.9 mJ

1.12 A unit of power used for electric motors is the horsepower (hp), equal to 746 watts. How much energy does
a 5-hp motor deliver in 2 hours? Express the answer in MJ. Ans. 26.9 MJ

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1.13 For t 0, q ¼ð4:0 10 Þð1 e 250t Þ (C). Obtain the current at t ¼ 3 ms. Ans. 47.2 mA

1.14 A certain circuit element has the current and voltage
i ¼ 10e 5000t ðAÞ v ¼ 50ð1 e 5000t ÞðVÞ
Find the total energy transferred during t 0. Ans. 50 mJ

1.15 The capacitance of a circuit element is defined as Q=V, where Q is the magnitude of charge stored in the
element and V is the magnitude of the voltage difference across the element. The SI derived unit of
capacitance is the farad (F). Express the farad in terms of the basic units.
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Ans.1 F ¼ 1A s =kg m 2