EECS
2015+1-1,2,3+all.pdf

Therefore tasers and other stun guns can immobilize

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Therefore, Tasers and other “stun guns” can immobilize the person for several minutes. The exact magnitude of the current at the Let-Go threshold is ü Reportedly, higher for males than for females ü Widely varies among individuals ü Depends on the frequency of the electric voltage. Ironically, the Let-Go threshold (see the numbers in Figure 1) is the lowest at the frequencies, which are chosen for industrial and household power distribution ü 60 Hz in North America ü 50 Hz in Europe and many other parts of the world. The Let-Go threshold is ~5-fold higher ü For DC (zero frequency) and ü At 10 kHz. <Sidebar> The Let-Go threshold is the lowest at the 50 – 60 Hz frequencies, which are chosen for industrial and household power distribution. For DC (zero frequency) and at 10 kHz, the threshold is ~5-fold higher. The muscle paralysis caused by electric current is also dangerous for the following reason: if you see another person “frozen on the circuit” and touch his/her body trying to help, you can get “frozen on the circuit” yourself! The best course of action is to interrupt the current from the power source to the victim’s body and only then touch the victim. T HE DANGERS TO VITAL FUNCTIONS OF THE HUMAN BODY BREATHING AND HEARTBEAT Another kind of muscular paralysis can occur in the diaphragm (which controls the breathing) due to electric currents above 15 mA. Some victims experienced difficulty breathing even at lower currents. The human heart malfunctions at electric currents above 50 mA: instead of regular contraction, the heart fibrillates and fails to send the blood to the arteries. Figure 2 compares the electrocardiograms under the condition of ventricular fibrillation and of the normal heartbeat. Book Page 96
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EE for the 21 st century 1-2 Safety: Avoid electrocution 1-2-1 Harm from currents © 2015 Alexander Ganago Page 6 of 8 Last printed 2015-07-24 11:59 AM File: 2015 1-2-1 Harm.docx Figure 2. Electrocardiograms of the heart in ventricular fibrillation (top) and of the normal heartbeat (bottom). Source: All these harmful events take place at current levels, which are very low compared to those found in many household and industrial sources. For example: ü An old C-type battery can produce 1 A current Now, you might ask how we can safely handle an old C-type battery without wearing rubber gloves? What protects our bodies from deadly electric currents from the outside? To answer these questions, we have to consider the electric resistances of various parts of the human body: see the next Unit. Book Page 97
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EE for the 21 st century 1-2 Safety: Avoid electrocution 1-2-1 Harm from currents © 2015 Alexander Ganago Page 7 of 8 Last printed 2015-07-24 11:59 AM File: 2015 1-2-1 Harm.docx T YPICAL QUESTIONS FOR SELF - ASSESSMENT 1 If the current, which flows from a hot wire through the human hand, exceeds the Let-Go threshold, the person cannot open his/her clenched fist due to the initial shock, but some time later, he/she would adapt and become able to open the fist even if the electrical excitation continues.
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  • Fall '07
  • Ganago
  • Electric charge, Alexander Ganago

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