IST Electrical and Electronic Knowledge 5

Question 1

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

Accepted Answer

Swap any two of the three line leads

Answer

Interchanging any two supply phases reverses the rotating magnetic field.

Question 2

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

Accepted Answer

It increases

Answer

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

Question 3

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

Accepted Answer

Zener diode

Answer

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

Question 4

Which AWG copper wire has the largest diameter?

Accepted Answer

4 AWG

Answer

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

Question 5

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

Accepted Answer

Apply lockout/tagout and verify zero energy

Answer

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

IST - Industrial Skills Test Practice Test