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Comp TIA A Certification Essentials Mercy Vocational High School

Electrical Safety. Note: Electricity can be dangerous. If you don't follow proper safety precautions , electricity could kill you.Current can killCurrent not voltage , is what causes the danger. Even a small amount of current passing through your heart can be sufficient enough to cause ventricula

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Comp TIA A Certification Essentials Mercy Vocational High School

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    1. Comp TIA A+ Certification Essentials Mercy Vocational High School Instructor: Mr. Maphorisa 2007/2008

    2. Electrical Safety Note: Electricity can be dangerous. If you dont follow proper safety precautions , electricity could kill you. Current can kill Current not voltage , is what causes the danger. Even a small amount of current passing through your heart can be sufficient enough to cause ventricular fibrillation or stop your heart entirely. A dangerous level of current is possible even with low voltage sources, such as a 9 v battery. The 1-10 100 rule The 1-10-100 rule states that you can feel 1 mA (milliamp, or 1/1000 amp) of current through your body, 10mA is sufficient to make muscles contract to the point where you cant let go of a power source, and 100 mA is sufficient to stop your heart . This rule is a rule you should learn and respect. Calculating current Current, Voltage and resistance are related through the following formula:

    3. Electrical Safety In this formula , V is voltage in volts (v) , I is current in amps (A) and r is the resistance in ohms. At a given voltage , current increases as resistance drops. A dangerous level of current can be reached if resistance is reduced sufficiently. Resistance of a human body The human body has resistance of about 500kOhms. This value is a somewhat ideal figure for contact with a small area of dry skin. Moisture and sweat on your skin will lower the resistance to a value nearer 5000 Ohms. Contact with a greater area of skin , e.g. gripping a wire btn your fingers or grasping a pipe, will further reduce resistance. If you were immerse your hand or foot , or puncture the skin so that the electrical connection is made with more conductive blood and tissue , the resistance could be a low as 100 ohms.

    4. Safety Precautions You should always follow common sense safety precautions to avoid electric shock. Dont touch exposed electrical wires Touch only insulated handles and parts of tools, probes, cords and so forth Leave covers on equipment unless u need to access internal components. Work one handed. If you use one hand electricity is likely to flow through your body and possible cause electric shock or death. Never Insert anything on the wall outlets other than a power cord. Jewelry are prone to electric shock Keep your hands clean and dry. Dont work with electricity in wet surroundings, especially wet floors

    5. Electrical measurements

    6. Multimeters Multimeters are devices used to measure: Current, resistance and voltage. The figure above shows an analog multimeter and a digital one. To measure each parameter you have to select the right setting using the dial in the middle of the meter.

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