2.1.3

What to expect 

How much energy do you use in your daily life? When you flip on a light switch or use a hair dryer, how much does that increase your energy consumption? These are questions that we are going to answer today. During this activity, we will investigate our electrical energy consumption using a device that measures electrical power and energy. 

Connections

In the previous activities, we have seen different forms of energy and electricity generation. In this activity, we will investigate the amount of electrical energy consumed by different kinds of devices. In the next few weeks after this, we will explore one type of renewable electricity generation in more detail: solar energy. 

Materials (per group of about 3 students)

• 1 Electricity Meter and extension cord

• Light Bulb Socket with cord and on/off switch

• Phone to use as a stopwatch

Test Devices (shared between groups)

• Incandescent Light Bulb

• LED Light Bulb

• RGB remote-control LED Light Bulb 

• Halogen Light

• Hair Dryer

• Plug-in electrical device of your own (optional)

Instructions

This activity contains two parts. First, we will use the  Electricity Meter to measure how much power different electrical devices consume, how much energy they use, and how much money they cost to operate. Second, we will use the micro:bit to measure the light output from each light bulb and compare their light output to their power consumption.  

Part 1: Measuring Power, Energy, and Cost

1. Plug the Electricity Meter into an electrical outlet. Use the extension cord if necessary.

2. Press the “M” button on the Electricity Meter repeatedly to view all of the measurement screens: Power (W), Energy (KWh), Voltage (V), Current (A), Power Factor (PF), Price of electric energy ($/KWh), and Total Cost ($). 

3. Use the “M” button to scroll to the Energy (KWh) screen. If it is not zero, press and hold the “M” button for 3 seconds to clear any previous data from the meter. 

4. Connect one of the Test Devices (a light bulb, halogen lamp, hair dryer, or a device that you brought yourself) to the Electricity Meter. Use the Light Bulb Socket if necessary. 

5. Use the Electricity Meter to measure how much power in Watts (W) the device consumes.

6. Using your phone as a stopwatch, measure how much energy (KWh) the Test Device consumes over 5 minutes. 

7. The average price of electricity in Chicago is $0.173 / KWh (that’s 17.3 cents per KWh). How much did it cost to operate the device for 5 minutes? Hint: it will be a very small number, but it adds up over time! 

8. On a blank piece of paper, keep track of the devices that you tested, the amount of power (W) that it consumed, the energy (KWh) it consumed over a 5-minute test, and the cost of the energy used for the test. 

9. Repeat the test for several different Test Devices and compare them. Which one used the most energy and cost the most money to operate?

In this part, you should have seen that different devices consume different amounts of power and energy. You may have noticed that in general, devices that produce a lot of heat tend to consume more energy and cost more money to operate. Some light bulbs produce more heat than others, making them more expensive to operate. But what about the actual light output of the light bulbs? In Part 2, we will use the micro:bit to measure the amount of light produced by each light bulb.

Part 2: Let's Talk Lights

In last week's activity, you saw that the micro:bit can use its built-in array of LEDs to measure brightness on a scale of 0 (dark) to 255 (very bright). The programming to do this is very simple. In this test, you will use a micro:bit to measure the brightness of each light bulb.

How does the code work?

When button A is pressed, the micro:bit shows a picture of a light on the LEDs and takes a reading of the light level, saving it as a variable called “Level”. Every time you press button A, it will save a new measurement to the variable “Level”. When button B is pressed, the micro:bit shows the value of the saved light level variable, “Level”. 

1. If you get stuck on the code, ask your friends or teacher for help. If you are still having trouble, you can access the complete code here: https://makecode.microbit.org/_P4CDY31KzHEC. After going to the link, click on "Edit" to use the code. 

2. Download the code to your micro:bit by connecting the USB cable to your computer and micro:bit, then pressing the purple “Download” button on the lower left corner of your MakeCode screen. Then drag the file from your computer’s Downloads folder to the micro:bit.

3. Select one of the light bulbs from Part 1, plug it in, and turn it on.

4. Take several light level measurements with the micro:bit. Try to keep the distance from the bulb consistent.

5. On a piece of scratch paper, record the average light level measurement from each bulb. 

6. Repeat the test for several different light bulbs. Which one was brightest? What was the difference in brightness levels between the different bulbs?

As you compared the brightness levels between the incandescent and LED bulbs, you probably noticed that the brightness levels were similar between them. However, in Part 1 you saw that incandescent bulbs consume a lot more power and energy than the LED bulbs. So, which would you rather install in your home? 

Think about it

In this activity we measured the power and energy consumption of some commonly used devices like light bulbs and hair dryers. We calculated and compared how much money it costs to operate each of these devices. Finally, we measured the amount of light that is actually produced by each light bulb, and compared the light production to the energy consumption.  

1. Were you surprised by the cost of running the devices?

2. Why would you prefer to use either the LED, incandescent, or halogen light bulbs?

3. If you were creating a warming heat lamp for a litter of kittens or puppies, which device would you use?

4. Which light bulb would you recommend to your parents based on your findings? Why?

Feedback link: Click here to provide feedback on this activity.

Next Time

In the next activity, you will get hands-on experience using solar a.k.a. “photovoltaic” cells. First, you will measure the output from solar cells in different kinds of circuits. Then you will use the electricity produced by the solar cells to power an electric motor and create “spin art”.