Daily Facts
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Electric Shock Voltage and Current

June 22nd Fact-of-the-Day

High-voltage is dangerous because human contact with high-voltage can cause a dangerous amount of current to flow through human tissues. Current does the damage, but the focus is on voltage, because voltage causes current. The amount of current of course depends not only on the amount voltage, but also on the amount of human resistance. Human resistance varies widely from person to person and with the same person from time-to-time. Someone who has just come out of swimming pool with wet hands and bare wet feet will have much lower resistance than someone with dry callused hands wearing dry rubber boots. Voltage sufficient to kill the first person might cause only a mildly unpleasant shock to the second one. The human current sensation threshold is about 1 ma. 10 to 20 ma is enough to cause 'can't let go' muscle contractions. 100 to 300 ma causes ventricular fibrillation and generally is fatal if continued. Measure the resistance of your body with an ohmmeter, calculate the amount of voltage required to produce 1 ma, and consider any voltage higher than that dangerous under current skin conditions. ©2005 Martek International All rights reserved.

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