Lesson Plan Industry Sector
Engineering & Design

AC/DC what's the difference?

Lesson Plan Overview / Details

Students will be introduced to the theory behind the two sources of electrical power. They will be given a chance to build on prior knowledge of direct current circuits and then expand that knowledge to include the workings of alternating current circuits. This lesson will provide a base for understanding direct current circuits the remainder of the year.

1 Class Period
60 Minutes

Objectives and Goals

• Students are able to recognize characteristics of alternating current (AC) and how it is generated; the characteristics of the sine wave; the basic characteristics of AC circuits.
• Students are able to interpret both AC and DC circuits.
• Students are able to demonstrate an understanding of the difference between AC and DC circuits by written expression of ideas.
• Students are able to show an understanding of the past of the development of electricity in the United states by written expression of ideas.

Activities in this Lesson

• AC/DC Rocks! - Hooks / Set

Begin class with the Iron Man 2 video below featuring the band AC/DC. As the students watch the video have them do a quickwrite to guess what the band name stands for, where it came from, and why it would be appropriate to choose this band to do music for the Iron Man movie? (Malcolm and Angus Young developed the idea for the band's name after their older sister, Margaret Young, saw the initials "AC/DC" on a sewing machine. "AC/DC" is an abbreviation for "alternating current/direct current". The brothers felt that this name symbolized the band's raw energy, power-driven performances, and a love for their music.) Use this discussion as a transition into today's lesson of the difference between AC and DC power.

• Review of DC - Lecture

Most students will be familiar with direct current power and how batteries produce electricity chemically. Some however may not, and others could use a refresher. Quickly go through the short portion of the PowerPoint on the elements of a DC circuit and intro to potato activity.

• Building a DC circuit - Demo / Modeling

Although this activity is said to have been originally set up for elementary school students, it makes a nice quick review activity for high school students to review the components of a DC circuit. The explanation of the activity will make much more sense to high school students and they should be far more able to properly use a multi-meter without assistance. Overall, using this activity with high school students will allow it to move quicker, but at the same time maintain a hands-on approach to learning.

*Note- If you struggle to get a functional circuit you may want to add a resistor of about 100 ohms.

• Teach Engineering Potato Power
• As students complete their DC circuits, they are then ready for some relatively new material on how AC is made and functions. Use the following website with its visual aid to describe how AC power is generated. Be sure to point out the sine wave, what is represents, etc. Describe the role of the magnets and their relation to the voltage alternating from positive to negative. Discuss various forms of mechanical energy that can be used to crank an AC generator (wind, water, steam, gas, etc). Don't forget to discuss how AC power can light a bulb, but is not good for electronics.

• How AC generators work Website with good visual of AC power generation
• As you go through the description of the website, use a method available to you to intermittently check for student understanding. In my class we use Turning Point student response remotes. The attached questions are designed to work with that system, but could be adapted for whatever is available in your room. Make sure to loop back for anything that polls poorly for understanding.

• After the students have had a chance in class to review DC circuits and begin to explore AC power, they are then ready to take that knowledge a bit further in some reading and discussion. If time remains, or for homework, have students read the following article on the progression of electricity grids in the United States.

• Power Wars website