Can someone please answer this problem? A common three-way bulb has two filament
ID: 1716353 • Letter: C
Question
Can someone please answer this problem?
A common three-way bulb has two filaments and is wired with three contacts in its base. When used in a three-way lamp, the switch successively sends current first through a high-resistance filament to produce a dim bulb, then through a lower resistance filament to yield a brighter bulb, and finally through both filaments to give the highest brightness bulb. If a particular three-way bulb is rated at 40-, 60-, and 100-watts power and is operated as part of a circuit delivering 120 V, how much current is drawn by the light fixture when used on each of the three possible power/brightness settings? If the bulb is left on for 90 minutes in the second switch position, how much energy, measured in both joules and kilowatt-hours, does it consume? If the local cost of electrical energy is $0.08 per kWh, how much does it cost the homeowner to run the lamp for this period of time?Explanation / Answer
a) The current drawn in each power is 40/120, 60/120 and 100/120 amperes respectively.
b) The power drawn in the second switch position is 60 watts and hence the energy is 60*90/(60*1000) = 0.09kWh and the cost is 0.09*0.08 = $0.0072.