Electrical Theory & Principles Flashcards
7 cards from real NECA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Theory & Principles flashcards as text
What principle explains why current flows when two points in a circuit have different electric potentials?
Answer: Potential difference drives charge from higher to lower potential
Electric current flows from higher to lower potential (conventional current) because charges move down the potential gradient, similar to water flowing downhill.
In a balanced 3-phase wye (Y) circuit with a line voltage of 208V, what is the phase voltage?
Answer: 120 V
In a wye system, phase voltage = line voltage / √3 = 208 / 1.732 ≈ 120 V.
What is the primary difference between real power and reactive power?
Answer: Real power does useful work; reactive power oscillates between source and load
Real power (watts) performs actual work, while reactive power (VAR) cycles back and forth between the source and inductive/capacitive loads without doing useful work.
The dielectric material in a capacitor primarily serves to:
Answer: Increase capacitance and withstand voltage between plates
A dielectric insulator between capacitor plates increases capacitance by reducing the electric field effect and allows the capacitor to withstand higher voltages without breakdown.
What happens to inductive reactance when frequency doubles?
Answer: It doubles
Inductive reactance XL = 2πfL is directly proportional to frequency, so doubling frequency doubles the inductive reactance.
Which of the following best describes the concept of electric power factor correction?
Answer: Adding capacitive or inductive loads to bring current and voltage closer to phase
Power factor correction involves adding capacitors (or sometimes inductors) to offset reactive loads, bringing current and voltage closer to in-phase and improving system efficiency.
A conductor's resistance increases with rising temperature due to:
Answer: Decreased electron mobility from increased atomic vibrations
As temperature rises, atoms in the conductor lattice vibrate more vigorously, impeding electron flow and increasing resistance — described by the temperature coefficient of resistance.