Solution Manual For Introduction to Chemical Engineering Thermodynamics 9e J.M. Smith, Mark Swihart

Solution 1.1 Problem Statement

Electric current is the fundamental SI electrical dimension, with the ampere (A) as its unit. Determine units for the following quantities as combinations of fundamental SI units. (a) Electric power (b) Electric charge (c) Electric potential difference (d) Electric resistance (e) Electric capacitance

Solution

(a) Power is power, whether it is electrical, mechanical, or otherwise. Thus, electric power has the usual units of power: power 

energy J N m kg m 2    time s s s3

(b) Electric current is by definition the time rate of transfer of electrical charge. Thus current 

or

charge time

charge  current*time  A s

(you probably recall that the Coulomb is the usual derived unit of charge, defined as 1 A s)

Solution continued on next page…

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