Electrical Theory & Principles Flashcards

What happens to the total resistance when resistors are connected in parallel?

Answer: It is always less than the smallest resistor

In a parallel circuit, the total resistance is always less than the smallest individual resistor because current has multiple paths to flow through.

Which law states that the algebraic sum of all currents entering and leaving a node equals zero?

Answer: Kirchhoff's Current Law

Kirchhoff's Current Law (KCL) states that the sum of currents entering a junction equals the sum of currents leaving it, based on conservation of charge.

A capacitor in a DC circuit, after fully charging, acts as:

Answer: An open circuit

Once fully charged, a capacitor blocks DC current because no more current flows when the capacitor voltage equals the source voltage, effectively acting as an open circuit.

What is the unit of magnetic flux density?

Answer: Tesla

Tesla (T) is the SI unit of magnetic flux density, defined as one weber per square meter (Wb/m²).

In an AC circuit, when voltage and current are in phase, the power factor is:

Answer: 1

A power factor of 1 (unity) occurs when voltage and current are perfectly in phase, meaning all power delivered is real (active) power with no reactive component.

The phenomenon where a changing magnetic field induces a voltage in a conductor is called:

Answer: Electromagnetic induction

Electromagnetic induction, discovered by Michael Faraday, is the production of an EMF (and thus a current) in a conductor exposed to a changing magnetic flux.

What is the reactance of a 10 mH inductor at 60 Hz?

Answer: 3.77 Ω

Inductive reactance XL = 2πfL = 2π × 60 × 0.010 = 3.77 Ω.