# Air Force Colors (3) Pacifc and Home front 1942-47

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33 A but not as 1 13 A. There are many circuits, often called networks, which are not series–parallel connections and to which the methods indicated will not apply. These must be solved by more advanced circuit theorems, which are beyond our scope at this stage. However, the vast majority of the circuits encountered by the electrical craftsman of the series, parallel or series–parallel type. 13 Summary of formulas for Chapter 1 Q Q t= t I where Q = electric charge, C; I = current, A; and t = duration of current, s.

Energy and work Energy and work are interchangeable, energy being used to do work. Both are measured in terms of force and distance. The SI unit of force is the newton (N), and the unit of distance or length is the metre (m). If a force moves through a distance, work is done and energy is used. 4 A force of 2000 N is required to lift a machine. How much energy is required to lift the machine through 3 m? workdone = distance × force = 3 × 2000 joules = 6000 J This work is mechanical, but we shall see that work can also be electrical.

A photocell causes a current of 4 µA in its associated circuit, and would take 1000 days to dissipate an energy of 1 mJ. What EMF does it provide? An electric blanket is required to provide heat energy at the rate of 7200 J/min from a 230 V supply. What current will flow? If the total resistance of an earth fault loop is 4 , what current will flow in the event of a phase-to-earth fault from 230 V mains? During a flash test, a voltage of 20 kV is applied to a cable with an insulation resistance of 5 M .