Electrical Theory & Principles Flashcards

Three equal resistors of 30 Ω each are connected in parallel. What is the total resistance?

Answer: 10 Ω

For equal resistors in parallel, total resistance = R/n = 30/3 = 10 Ω.

What is the primary purpose of a transformer in electrical systems?

Answer: Step voltage levels up or down via electromagnetic induction

Transformers use mutual induction between primary and secondary coils to step AC voltage up or down while inversely affecting current.

In a 3-phase system, the voltage between any two line conductors is called:

Answer: Line voltage

Line voltage is measured between any two of the three phase conductors, and in a balanced wye system it equals phase voltage multiplied by √3.

What type of energy is stored in a magnetic field around an inductor?

Answer: Electromagnetic (magnetic) energy

An inductor stores energy in its magnetic field, expressed as E = ½LI², where L is inductance and I is current.

Which of the following materials is classified as a semiconductor?

Answer: Silicon

Silicon is a semiconductor with electrical conductivity between conductors and insulators, making it fundamental to electronic devices and solar cells.

The time constant (τ) of an RC circuit determines:

Answer: How quickly the capacitor charges or discharges

The RC time constant τ = R × C defines the time for the capacitor to charge to approximately 63.2% (or discharge to 36.8%) of its final value.

Apparent power in an AC circuit is measured in:

Answer: Volt-amperes (VA)

Apparent power (S) is the product of RMS voltage and RMS current (S = V × I) and is expressed in volt-amperes (VA) to distinguish it from real power in watts.