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DC Vs. AC Voltage Safety

In the 1890s, before cities became electrified, Thomas Edison argued that alternating current (AC) was dangerous and that direct current (DC) was safe. In fact, both AC and DC can be dangerous, although AC is more hazardous at lower voltages.

  1. Description

    • A direct current is a steady flow of electricity at a constant voltage, as from a battery. The flow of alternating current reverses direction 60 times a second. Alternating current allows the use of transformers for efficient distribution of electric power.

    Household DC

    • Most DC sources in the home are too weak to give a shock to dry skin. Toys, flashlights, and MP3 players use dry-cell or rechargeable batteries for power. These small devices usually run on between 3 and 12 volts and are almost universally safe.

    Household AC

    • The electricity that comes from the wall outlet is 110 volt AC power. This is enough to give a painful but not lethal shock to the dry skin of a healthy adult, but it may kill a small child. The danger is greatly increased if a person's skin is wet, and if the current isn't disconnected immediately.

    Sweating

    • While both AC and DC can induce high currents in a person's body at high voltages, the frequency of AC induces sweating. Sweating lowers skin resistance and sets the stage for a stronger shock.

    Muscle Spasms

    • A strong electric current flowing through skin will cause muscles to contract. This leads to breathing difficulty and uncontrolled heart contractions. The 60 cycle-per-second fluctuations of AC current make muscle contractions more severe.

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