Some Electrical Circuit Considerations

Abstract

In Section 6 of Chapter 13 we found the current through the crystal for a prescribed driving voltage across the crystal. In electrical engineering terminology we have found the admittance of the crystal [(⁴³), Chapter 3, Section 18)]. However, before we can introduce these terms properly we must discuss a sign convention associated with the terminology. The sign convention we will employ is contained in the diagram in Fig. 24, which indicates that by convention the current is considered positive if it flows from active to passive + to + [(⁴³), Chapter 9, Sections 1, 2]. The passive element can be represented by an admittance Y and eliminated from the diagram by means of the relation

$$I = YV $$

((15.1))

, so that we may consider the diagram in Fig. 25 instead of the one in Fig. 24. Thus it is clear that our formula for surface charge has effectively determined the admittance of the crystal, which, in that case, was a passive element.