A compact fluorescent light (CFL) bulb is very energy-efficient. A 22W CFL bulb has the same brightness as a 100W incandescent bulb. (Note that these calculations ignore the fact that the CFL bulb can last up to 10 times as long as the incandescent bulb. This would increase your savings even more.)
- a. If you have this light bulb on for 5 hours a day, for 350 days during a year, how many hours is it on?
- b. A kilowatt is 1000 watts. The kilowatt-hour is a common unit for energy, obtained by multiplying the power in kilowatts by the time used in hours. How many kilowatt-hours (kWh) will you use when burning the 100W bulb for the year (don’t forget to convert the 100W to kW first)?
- c. How many kilowatt-hours (kWh) will you use when burning the 22W bulb for the year (be sure to convert the 22W to kW before multiplying by the time in hours)?
- d. Assuming that the cost of electricity is 15¢ per kWh, what is the cost of using the 100W incandescent bulb for the year?
- e. Assuming this same cost, what is the cost of using the 22W CFL bulb for the year?
- f. How much do you save per year by using the 22W CFL bulb?
- g. How much would you save every year if you replaced 20 of the 100W incandescent bulbs with the 22W CFL bulbs?
(a)
The number of hours the light bulb is on.
Answer to Problem 3SP
The number of hours the light bulb is on is
Explanation of Solution
Given info: Light bulb is on for 5 hours a day for 350 days during a year.
The number of hours the light bulb is on is,
Conclusion:
The number of hours the light bulb is on is
(b)
The number of kilo-watt hours used when the light bulb is on for a year.
Answer to Problem 3SP
The number of kilo-watt hours used when the light bulb is on for a year is
Explanation of Solution
Given info: Light bulb is on for 5 hours a day for 350 days during a year.
From (a), the number of hours the light bulb is on is
The number of kilo-watt hours used when the light bulb is on for a year is,
Conclusion:
The number of kilo-watt hours used when the light bulb is on for a year is
(c)
The number of kilo-watt hours used when the 22 W light bulb is on for a year.
Answer to Problem 3SP
The number of kilo-watt hours used when the 22 W light bulb is on for a year is
Explanation of Solution
Given info: Light bulb is on for 5 hours a day for 350 days during a year.
From (a), the number of hours the light bulb is on is
The number of kilo-watt hours used when the 22 W light bulb is on for a year is,
Conclusion:
The number of kilo-watt hours used when the 22 W light bulb is on for a year is
(d)
The cost of using 100 W bulb for a year.
Answer to Problem 3SP
The cost of using 100 W bulb for a year is
Explanation of Solution
Given info: Cost of electricity is
From (b), number of kilo-watt hours used when the 100 W light bulb is on for a year is
The cost of using 100 W bulb for a year is,
Conclusion:
The cost of using 100 W bulb for a year is
(e)
The cost of using 22 W bulb for a year.
Answer to Problem 3SP
The cost of using 22 W bulb for a year is
Explanation of Solution
Given info: Cost of electricity is
From (b), number of kilo-watt hours used when the 22 W light bulb is on for a year is
The cost of using 22 W bulb for a year is,
Conclusion:
The cost of using 22 W bulb for a year is
(f)
The savings per year while using 22 W CFL bulb.
Answer to Problem 3SP
The savings per year while using 22 W CFL bulb is
Explanation of Solution
Given info: Cost of electricity is
The savings per year while using 22 W CFL bulb is the difference between the cost of using 100 W and 22 W bulbs. Therefore, the saving is given by,
Conclusion:
The savings per year while using 22 W CFL bulb is
(g)
The savings per year while twenty 100 W bulbs are replaced by 22 W CFL bulb.
Answer to Problem 3SP
The savings per year while twenty 100 W bulbs are replaced by 22 W CFL bulb is
Explanation of Solution
Given info: Cost of electricity is
The savings per year while using 22 W CFL bulb is
Conclusion:
The savings per year while twenty 100 W bulbs are replaced by 22 W CFL bulb is
Want to see more full solutions like this?
Chapter 1 Solutions
Physics of Everyday Phenomena
Additional Science Textbook Solutions
Integrated Science
Physical Universe
Applied Physics (11th Edition)
University Physics Volume 2
Loose Leaf For Explorations: Introduction To Astronomy
- In 2019, residential customers in the United States purchased an average of 10,649 kilowatt-hours of electricity. (a) What is the average daily electricity consumption for a residential customer? (b) How many 50W light bulbs could you run flat out for a 24hr period with this electricity? (c) If this energy was instead only used to run a 1,000W microwave after how many hours would the microwave stop?arrow_forwardA microwave oven has a power requirement of 1,248 W. A frozen dinner requires 5.0 min to heat on full power. (a) How much electrical energy (in kWh) is used? (b) If the cost of electricity is 11¢ per kWh, how much does it cost to heat the dinner? (Do not round your final answer. Fractional cent values are acceptable.)arrow_forwardA 400 W immersion heater is placed in a pot containing 2.00 L of water at 20C. (a) How long will the water take to rise to the boiling temperature, assuming that 80% of the available energy is absorbed by the water? (b) How much longer is required to evaporate half of the water?arrow_forward
- A light bulb uses up a power of 2.6 kW/hr. If the rate is Php153.42 per 1 kW/hr, and the light was on for 24 hours, a. How much kilowatt hour was consumed? b.How much was the bill after 24 hours?arrow_forwardA 2 kg toy car can drive at a constant speed of 20 km/hr, please: a. Calculate the kinetic energy at this speed.b. Assume the same kinetic energy is delivered by a 12 V battery and the electrical resistance of the toy car is 2 Ω, what is the corresponding electrical current?Hint: equations to use (1) P= E/t, (2) P=VI, (3) V=IRarrow_forwardA light-rail commuter train draws 630 A of 650-V DC electricity when accelerating. (a) What is its power consumption rate in kilowatts? (b) How long does it take to reach 20.0 m/s starting from rest if its loaded mass is 5.30×104 kg , assuming 95.0% efficiency and constant power? (c) Find its average acceleration. (d) Discuss how the acceleration you found for the light-rail train compares to what might be typical for an automobile.arrow_forward
- Calculating the Cost Effectiveness of Compact Fluorescent Lights (CFL)If the cost of electricity in your area is 12 cents per kWh, what is the total cost (capital plus operation) of using a 60-W incandescent bulb for 1000 hours (the lifetime of that bulb) if the bulb cost 25 cents? (b) If we replace this bulb with a compact fluorescent light that provides the same light output, but at one-quarter the wattage, and which costs $1.50 but lasts 10 times longer (10,000 hours), what will that total cost be?arrow_forwardA constant current transfers 10*10^14 electrons onto one plate of a capacitor in 3 minutes [min]. (a) What is the current, in units of amperes [A]? Express the answer using an appropriate SI prefix such that there are only 1, 2, or 3 digits shown to the left of the decimal. (b) If the capacitor has a capacitance of microfarads [F], what is the voltage in units of volts [V] across the capacitor?arrow_forwardWhen running on its 11.4 V battery, a laptop computer uses 8.3 W. The computer can run on battery power for 9.0 h before the battery is depleted.a. What is the current delivered by the battery to the computer?b. How much energy, in joules, is this battery capable of supplying?c. How high off the ground could a 75 kg person be raised using the energy from this battery?arrow_forward
- (a) A pocket calculator draws 0.40 A of current when connected to a 6.0 V battery. At whatrate does the calculator use electrical energy? (b) An electric heater is to provide 14 kW ofpower when connected to a 120 V potential difference. What should the resistance of theheater be when turned on?arrow_forwardA typical cost for electric power is $ 0.135 per kilowatt-hour. (a) Some people leave their porch lights on all the time. What is the yearly cost to keep a 75-W bulb burning day and night? (b) Suppose a refrigerator uses 400W of power when it’s running, and it runs 8 hours a day. What is the yearly cost of operating that refrigerator?arrow_forward4.A 2-W light bulb is connected to a 6-volt battery and left on for 20 minutes. (a)What is the power (W) of the light bulb? (b)How much charge flows through the light bulb in this time? What total battery energy has been used?arrow_forward
- College PhysicsPhysicsISBN:9781938168000Author:Paul Peter Urone, Roger HinrichsPublisher:OpenStax CollegePhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning