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Safety Quiz

Helpful Information

1. Sources:
   Electrical Safety Foundation International.
   NIOSHA: Electrical Safety, Publication No. 2009-113.
   Values may differ depending on various factors including voltage, duration, wet conditions, body size, clothing, frequency, etc.
2. Source:
   Ohms Law article at wikipedia
3. Source:
   Hybrid Vehicle Measurement Safety Basics by Jack Rosebro
4. Sources:
   NIOSHA: Electrical Safety, Publication No. 2009-113.
   Ohm's Law article at All About Circuits.
   Yes, it's the current that can kill you, but it takes voltage to push that current through your body. How much voltage it takes depends mostly on the resistance of your body and how well grounded you happen to be. Your resistance can vary greatly depending on factors like metal jewelry, clothing, sweat, where your body contacts the live circuit, etc.
5. Sources:
   NIOSHA: Electrical Safety, Publication No. 2009-113.
6. When working with electricity it's usually best to be insulated from the ground. This will reduce the chances and severity of an electric shock. A good way to insulate yourself from ground is to place insulation between yourself and the ground. The insulation can be shoes (thicker is better), plywood (dry) or anything that will provide resistance between you and the ground. Gloves can also provide some insulation.
7. Some circuits can remain energized (usually by capacitors) even after pulling the power plug and turning off the power switch. Power indicator lights are rarely connected to every part of a circuit.
8. Shorting the leads on large capacitors can result in a bright flash, loud pop and enough heat to weld the contacts. Some capacitors can remain charged for weeks, even if they are disconnected and sitting on a shelf. The best way to discharge a capacitor is to connect a high value resistor (several kOhms) across the capacitor leads and let it sit for a while so it can completly discharge. Always sheck it with a volt meter to verify it has discharged.
9. The skin effect will increase the amount of current that passes over your skin, but it will not prevent current from entering your body and causing harm. Do not rely on it for protection.
10. Transformers use alternating current to induce current from the primary winding to the secondary winding. DC current will not effectively induce current into another winding. Transformers generally do not hold a charge.
11. A transformers current rating typically specifies the maximum allowable current it can continuously supply to the load. The actual current through the transformer is usually determined by the load.
12. Most capacitors are designed to hold a charge for as long as possible. All capacitors will eventually discharge due to leakage current between the plates and resistance between the leads. The time it takes a capacitor to discharge depends on several factors. Sometimes a very high value resistor is places between the leads to allow the capacitor to slowly discharge.
13. Almost all wire will have important information printed on the insulation. Most of the time the voltage rating and manufacturer will be printed. At the very least there should be a manufacturer name and some form of serial number, model number, or other code that can be used to get information about the wire from the manufacturer. The wire information is not printed, worn off, painted over, etc, it's best not to use the wire.
14. Tesla coils can be lethal!

All about Circuits - Electrical Safety is a good source of information.