WATTS UP??? Take-Home Lab

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Ralph Wade
7 years ago
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1 WATTS UP??? Take-Home Lab I. General Instructions: Name: We have a limited supply of Watt s Up machines, so don t keep the meter more than two nights. Make sure you document your work well since you so you don t have to take the machine home more than once. SHOW ALL YOUR WORK!!!!!! (calculations and units) II. How to use the Watts Up meter: 1. Using the meter is not dangerous. It is just like using an extension cord. However, if you unplug your microwave or VCR, you will have to reset the clock. 2. Unplug the appliance you are trying to test. Plug the Watts Up meter into the wall. IT WILL CLEARLY NOT FIT UNLESS THE WALL SOCKET IS A THREE-PRONG GROUNDED PLUG. The sockets in your kitchen should be grounded---so if you are testing a lamp or CD player, you may need to move it to the kitchen. 3. The Old Black Watts Up meter likes to reset itself to dollar amounts. If you think it is not working because it is reading zero, hit the MODE button once and there should be a dash next to the kw lettering, indicating that the Watt s Up is measuring in KiloWatts 5. The Watts Up machine measures in KiloWatts, so multiply the reading by 1,000 to get Watts.. I THINK the Kill-A-Watt machines measure in Watts. Use the first experiment to make sure you know how the machine works it is pretty simple once you figure it out.

2 Project #1: Calculating the Accuracy of the device: (5 points) 1. Test three different lamps in your home. Record the wattage of the bulb in the data table. If there are many bulbs, I recommend that you turn them on one at a time, add the total wattage of all the bulbs and compare this to the Watt s Up reading. Record the reading that the Watts Up machine reads. Calculate its percent error. Warning: the energy-efficient Compact Florescent Bulbs (CFLs) may tell you the equivalent wattages. For example: I purchased a 60 Watt CFL bulb that actually only uses 14 watts. Try to find the ACTUAL wattage of the bulb. You may have to unscrew the bulb and look on the base. The point of this section is just to make sure you know how the measuring tool works that you understand that.06 kw is the same as 60 Watts. It should not be difficult to find 3 different lamps. Even if you have a lot of recessed lighting, look for desk lamps, bedside table lamps, lava lamps, etc. Lamp # Bulb Wattage Watts Up reading Percent Error SHOW WORK FOR PERCENT ERROR. Assume Watts Up reading is more accurate reading. Continue work on next page. Watt' supwattage LampWattage PercentError = Watt' supwattage

3 ======================================================== Project #2: Testing Appliances and Looking for Leaking Electricity (Phantom Loads). (15 points) Many devices use electricity even when they are officially turned off. For example, your TV needs to keep some circuits on so that it can receive messages from the remote. I tested my CD player, and it used up some energy when it was set to CD and there was no CD spinning. Your goal in this project is to find out how many Watts of power six appliances use when off and on. Suggestions for appliances: TV, VCR, Computer Monitor, Computer CPU, Computer Speakers, Laptop cord WITHOUT THE LAPTOP ATTACHED!, CD player, answering machine, clock radio, hairdryer, laptop, toaster oven, coffee machine, blender, Cell Phone Charger, printer that is on but not printing, fax machine, answering machine, etc. Choose a nice variety of appliances from around your house. You need to make sure that at least TWO appliances registers wattage when it is turned off.

4 Appliance OFF Wattage (Watts) ON Wattage (Watts) Hint: If your cell phone charger or laptop transformer don t register any wattage on the machine, it may be less than.1 Watts. There is still a way to measure the Wattage if you have a Kill-A-Watt machine. Since power is also current*voltage, you can set the machine to current (probably get.01 Amps), set the machine to voltage (probably get between 110 and 120) and multiply the two numbers to get wattage. On the following page you will calculate the total cost per year for each appliance that draws a phantom load. Remember that a Joule is a VERY small unit of energy for human-scale machines. Thus, the power companies charge in KiloWattHours, which is the energy it takes to run 10 hundred- Watt Bulbs for one hour (or one thousand Watt bulb for an hour).

5 To calculate cost the year: a. Convert the Wattage of each appliance to KiloWatts. (Divide by 1,000). b. Calculate the number of hours in a year: 24 hours in a day, days in a year. SHOW WORK! c. Multiply the KiloWatts of each appliance by the number found above to calculate the total KiloWattHours used in one year. d. Multiply by.08 (dollars) to find the cost (in dollars). This is what Pepco charges. e. Write final answer in dollars and cents: $2.40. Work for Calculating hours in a year: Work for Cost of Appliance #1:

6 Work for Cost of Appliance #2: Calculating the actual energy used by One Appliance in 1 month. In this section, you will calculate the actual energy used by one of the five appliances. Because power plants and power lines are not 100% efficient, you are actually using more energy than you think you are. 1. Choose one of the five appliances you measured. Choose a laptop, TV, cell phone charger, etc. Choose an object you MIGHT leave on for a month. (or a month total averaged out for a year) Appliance chosen: 2. Calculate the Joules of energy used by the appliance in one month=30 days (Energy = Power * Time)

7 3. Most Power lines are 98 % efficient. Energy is lost in the heating of the wires and in the transformers that change the voltage from high to low voltage. Calculate the ACTUAL ENERGY that came from the power plant, if the number of Joules you calculated above is only 98% of the energy that came from the plant: 4. 50% of the energy it takes to turn the turbines in a power plant comes from coal. Coal plants are typically 33 % efficient (depending on the age of the plant). Some energy is always lost as exhaust heat (kind of like your car). Calculate the ACTUAL ENERGY (stored in the coal) if the number you found above was actually only 33% of the chemical stored energy in the coal. This is the actual energy used by your appliance in a month.

8 5. Calculate the pounds of coal used by the power plant. ASSUMING the power plant that generated your electricity was generating electricity from coal. Take your answer to question #4 and convert to pounds of coal: 29,302,000 Joules of energy = pounds of coal. 6. Use your answer to #4 to calculate the pounds of Carbon Dioxide that were emitted in the chemical reaction that released the energy to create the electricity: 1.8 x 10 6 Joules of energy = 1 pound of CO Calculate the number of trees that would be needed to absorb the CO 2 emitted by your device in a year. a. multiply your answer to #6 by 12 to get the pounds of CO 2 per year. b. Convert from pounds of CO 2 to # of trees: 1 tree = 16.5 pounds of CO 2. (Younger trees absorb more CO 2 than older trees, but one of the averages I found was that averaged over the life of a tree, one tree absorbs 16.5 pounds of CO 2 per year)

9 Project #3: Get Creative (8 points) I want you to find two devices that you can alter in some way while you are taking measurements to see how the wattage changes. Possible ideas: (you will definitely get points for being original) Run your hairdryer on different power settings. Set your blender to different settings. Set your toaster oven to different settings. Compare the wattage it takes to play a CD vs. radio, vs. cassette. Run a power drill with no load and while actually doing work. Measure your computer printer while it is not busy and while it is printing. Fill out the data table below. You need at least TWO different tests for each device, but I have made room for four. If you don t see any difference between two different settings, it means that the difference in power usage is less than the amount the meter can pick up. If you find no difference in a given device, find another item to test. Device: Situation One And Power Reading: Situation Two And Power Reading: Situation Three and Power Reading: Situation Four and Power Reading: Example: Hairdryer Low setting, Hot Air: 300 Watts Low setting, Cool Air: 275 Watts High setting, Cool Air: 400 Watts High setting Hot Air: 500 Watts

Measuring Electricity Class Activity

Measuring Electricity Class Activity Objective: To understand what energy is, how it impacts our daily lives, and how one can become an energy steward. Learning Outcomes: Students will: 1. Understand where