Question 1

Why is 400 Hertz AC used as the standard for aircraft power instead of the 50 or 60 Hertz used in homes?

Accepted Answer

Higher frequency power is used in aviation because it allows for the design of significantly smaller and lighter transformers and motors. Since weight is a critical factor in aircraft performance, bumping the frequency up to 400 Hertz enables engineers to achieve the same power output while saving a substantial amount of weight. However, this higher frequency also makes inductive and capacitive reactance more significant, which technicians must account for when analyzing circuits.

Question 2

What is the difference between "conventional current" and "electron flow" in aircraft circuit analysis?

Accepted Answer

Electron flow describes the actual physical movement of electrons, which travel from a negative charge to a positive charge because they are repelled by like charges. Conventional current is an engineering quirk that defines flow as moving from positive to negative. While electrons are the particles doing the actual traveling, most EASA Module 3 circuit analysis and diagrams use conventional current for mathematical consistency.

Question 3

How do series and parallel circuits differ in their impact on aircraft system reliability?

Accepted Answer

In a series circuit, all components are on a single path; if one component fails or a wire snaps, the entire circuit goes dead because the path is broken. Parallel circuits are the "workhorses" of aviation because they provide multiple paths for current. This architecture ensures that if one system fails—such as a galley coffee maker—it does not interrupt the power flow to critical systems like the primary flight displays, as each branch receives the full system voltage independently.

Question 4

What are Thevenin’s and Norton’s theorems, and how do they help a technician?

Accepted Answer

These theorems are used to simplify complex, linear electrical networks into basic equivalents. Thevenin’s theorem replaces a complex circuit with a single voltage source and a series resistor, while Norton’s theorem represents it as a current source in parallel with a resistor. These "summaries" allow a technician to predict how a specific component, like a new radio, will behave when connected to the aircraft's power grid without having to model every individual generator and load on the plane.

Question 5

What is the "Power Triangle" and why is it important for B2 technicians?

Accepted Answer

The Power Triangle represents the relationship between three types of power in an AC circuit: Real Power (Watts), which does the actual work; Reactive Power (VARs), which maintains magnetic and electric fields; and Apparent Power (VA), which is the total power the generator must provide. Technicians use this to calculate the Power Factor. A low power factor is inefficient because it means the system is drawing more current than necessary for the work being performed, leading to excess heat in the wiring.

EASA Module 3: Electrical Fundamentals for B2

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