Physics: Principles with Applications (7th Edition)

Published by Pearson
ISBN 10: 0-32162-592-7
ISBN 13: 978-0-32162-592-2

Chapter 18 - Electric Currents - Questions - Page 520: 9

Answer

a. 2a by 3a b. a by 2a

Work Step by Step

The resistance of the block can be calculated by $R=\frac{\rho L}{A}$. a. To minimize resistance, we want a small length and a large cross-sectional area. We do this by connecting wires to the 2 faces with the largest dimensions, 2a by 3a. This maximizes the area and minimizes the length. b. Similarly, to maximize resistance, we want a long length and a small cross-sectional area. This is accomplished by connecting the wires to the 2 faces with the smallest dimensions, a by 2a, which minimizes the area and maximizes the length.
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