An incandescent light bulb in a simple series circuit is rated to draw .50 amperes when 120 volts is placed
across its filament.
a. Determine the resistance of the filament when lit at its rated values.
b. Determine the wattage rating for this light bulb.
c. The light is left on for 2.0 hours per day. Electrical energy costs 19ç per kilowatt-hour. 1 kilowatt-hr =
3,600,000 joules). How much does it cost to keep this light bulb lit for a year?
d. The light bulb in this problem costs $1.50 and has a life time of 1460 hours. What is the total cost for
running this light bulb for 6.00 years at 2.00 hours per day?
An energy efficient light bulb in a simple series circuit is rated to draw .167A when 120V is placed across
the filament. This low watt light bulb gives off the same amount of light as the incandescent bulb from the
previous problem.
a. Determine the resistance of this light bulb at its rated values.
b. Determine the wattage rating for this light bulb.
c. The light is left on for 2.0 hours per day. Electrical energy costs 19ç per kilowatt-hour. 1 kilowatt-hr =
3,600,000 joules). How much does it cost to keep this light bulb lit for a year?
d. The light bulb in this problem costs $4.00 and has a life time of 4380 hours. What is the total cost for
running this light for 6.00 years at 2.00 hours per day?
©1999 Mark D. Greenman
Marblehead Science Matters – mgreenman2@verizon.net
PB#06
printed 8/5/12