HV Exit Exam • Set 5 Question 4 of 30
What range of 50/60 Hz AC electrical current flowing through the human body is generally recognized as the 'can't let go' threshold (tetanic muscle contraction)?
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Direct Answer
Option B: 9 to 25 mA
At 9 to 25 mA AC (typically ~10–16 mA for men, ~9–12 mA for women), involuntary muscle contraction prevents a person from releasing an energized conductor ('let-go threshold').
All Options
A
1 to 3 mA
B
9 to 25 mA
(Correct Answer)
C
50 to 100 mA
D
1 to 5 A
Detailed Explanation & Context
At 9 to 25 mA AC (typically ~10–16 mA for men, ~9–12 mA for women), involuntary muscle contraction prevents a person from releasing an energized conductor ('let-go threshold').
Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • High Voltage Safety Officer & Switchgear Operations (HV).
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