Regarding alternating current at domestic frequency compared with direct current of the same voltage, which statement is correct?
- A Alternating current is more dangerous because it causes tetanic spasm and the victim cannot let go ✓
- B Direct current is more dangerous because it produces sustained tetanic contraction
- C Both produce identical effects at equal voltage and duration
- D Alternating current is safer because it crosses zero 100 times per second
Correct answer: A. Alternating current is more dangerous because it causes tetanic spasm and the victim cannot let go
Explanation
Alternating current at 50 Hz is far more dangerous than direct current at equivalent voltage. It induces repeated tetanic contraction of muscles, and since flexor muscles overpower extensors, the hand grips the conductor involuntarily. The no-let-go threshold for AC is about 10 mA, whereas a much larger DC current is needed for a similar effect. DC tends to throw the victim off the circuit with a single violent contraction.
Reference: The Essentials of Forensic Medicine and Toxicology, K S Narayan Reddy, 34th ed.
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Written and medically reviewed by the StethoPrep medical team.