The third current electricity lab/activity relates power and energy usage to cost. Timing: This lab/activity should take about 30 minutes in class and 20 minutes at home to complete

Group Size: Small groups

Learning Objectives:

The objective of this lab/activity is to:
a) Introduce the following key concepts:
-Electrical energy
-Energy usage
b) Reinforce the following concepts from the previous lab work and units:


Guiding Question:

How does the wattage of an appliance relate to its monthly cost?


No materials required besides having appliances in the classroom. Anything with a wattage rating would work.


Read through the opening section as a class. Students should feel comfortable with the example calculation at the top of the table before they start looking for appliance ratings. Students will repeat the process at home. Have a fall back rate for students to use if they can’t find the electric bill.


The two tables should be graded for correctness (based on the given rates). There are three closure questions that students should complete at home.

Answer Key or Rubric:

1. In terms of wattage what was the most surprising home appliance? Why?
Varies, but microwaves usually win out.

2. Suggest some ways we could save electricity in your home.
Use energy efficient appliances… turn them off when not in use… etc...

3. If you replaced a 100W incandescent (regular) light bulb in your house with a 15W energy saving compact fluorescent bulb. How much would you save each month if you use the bulb for 700 hours each month and the energy company charges 30 cents and Kilowatt-hour?
85W x 700 hr / 1000 x $0.30 = $17.85

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