At 120 volts, the most common household current in the United States, a 100watt light bulb draws 0.83 amps. To calculate the amperage of a light bulb, one must divide the number of watts by the volts powering the circuit.
In order to reduce energy consumption, the 100watt light bulb is no longer available in the United States. In addition, light bulbs between 40 watts and 100 watts must meet the requirement that they are a minimum of 30 percent more efficient. This reduction in wattage also results in a reduction in amperage for light bulbs so that the replacement bulbs are safe for use with existing wiring.
The formula you are looking for is I = W/E. Amps = Watts divided by Volts.
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Power (Watts) = Current (Amps) * Voltage (Volts)
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W = V * A. Watts = Volts X Amps.
http://www.chacha.com/question/howmanyampsdoes...

1. Set the base of the bulb into the socket or receptacle of a lamp. Twist the bulb clockwise to screw the bulb into the receptacle on the lamp. Turn the bulb only until it resists
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