Electrical and Electronic Knowledge Flashcards

How do you reverse the rotation of a three-phase induction motor?

Answer: Swap any two of the three line leads

Interchanging any two supply phases reverses the rotating magnetic field.

What happens to the inductive reactance of a coil when the supply frequency increases?

Answer: It increases

XL = 2πfL, so reactance is directly proportional to frequency.

Which component is most commonly used to provide a stable reference voltage in a simple regulator circuit?

Answer: Zener diode

A reverse-biased Zener diode holds a nearly constant voltage across it at its breakdown rating.

Which AWG copper wire has the largest diameter?

Answer: 4 AWG

In the AWG system, smaller gauge numbers mean larger conductors.

Before a technician works on an energized motor circuit, what step is required first?

Answer: Apply lockout/tagout and verify zero energy

OSHA requires lockout/tagout and verification of a zero-energy state before servicing equipment.

In an NPN transistor used as a switch, what turns the transistor on?

Answer: Forward-biasing the base-emitter junction

Base current from a forward-biased base-emitter junction allows collector-to-emitter current to flow.

In PLC ladder logic, an XIC (Examine If Closed) instruction is true when its input bit is:

Answer: 1 (on)

XIC passes logic continuity when the referenced bit is set to 1.