CHAPTER 2 Power Theory in Electrical Circuits

1. Introduction

Defining the concept of power means opening a can of ‘scientific worms’.

Griffiths (2013:357) defines power as the rate of work:

Power= dW dt = v ( EJ )dt

where work or energy E · J is deployed in per unit (p.u.) time and volume (i.e., energy has both time and space attributes).

However, Lehrman wrote a paper entitled “Energy is Not the Ability to Do Work” (Lehrman, 1973).

Valkenburg (1964) defines power as only a time-derivative of energy:

p= dw dt

He factorizes the expression for the time derivative of energy into a product of voltage and current:

dw dt = dw dq × dq dt =vi

Einstein’s definition of energy

E=m c 2

has long been ...

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