CET CET Power Supplies and Electrical Safety 2

Question 1

What current level through the human body is generally considered the threshold for causing ventricular fibrillation?

Accepted Answer

100 mA

Answer

Approximately 100 mA through the chest region for more than a fraction of a second can induce ventricular fibrillation, which is fatal without defibrillation.

Question 2

What does a Ground Fault Circuit Interrupter (GFCI) outlet protect against?

Accepted Answer

Electric shock from current leaking to ground through a person

Answer

A GFCI monitors the difference between hot and neutral currents; if more than ~5 mA is unaccounted for (leaking through a person), it trips within milliseconds.

Question 3

What is the function of a Metal Oxide Varistor (MOV) in a surge protector?

Accepted Answer

Clamp transient overvoltages by conducting heavily when voltage exceeds a threshold

Answer

An MOV has a highly non-linear resistance that drops sharply at its clamping voltage, diverting surge energy away from protected equipment.

Question 4

What IEC safety class designates equipment with double insulation that requires no protective earth ground connection?

Accepted Answer

Class II

Answer

IEC Class II equipment uses double or reinforced insulation and bears the square-within-a-square symbol; no earth ground pin is needed.

Question 5

Why are bleeder resistors used in high-voltage power supply circuits?

Accepted Answer

Discharge filter capacitors when power is removed, preventing electric shock

Answer

Bleeder resistors provide a discharge path for stored capacitor charge so the output voltage decays to a safe level when the supply is turned off.

(CET) Certified Electronics Technician Practice Test

(CET) Certified Electronics Technician Practice Test

CET CET Power Supplies and Electrical Safety 2