AC/DC what's the difference? :: Curriculum

Engineering Technology (Robotics) Model

Units:

AC/DC what's the difference?

Part of Unit: Theory, Measurement, Control, and Applications of Electrical Energy

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.

Time

1 Class Period: 60 Minutes

Standards

California Career and Technical Education Standards

California Academic Content Standards (Reinforced)

ELA.9-10.R.CAGT.2.5 Extend ideas presented in primary or secondary sources through original analysis...3
ELA.9-10.R.CAGT.2.6 Demonstrate use of sophisticated learning tools by following technical direction...2

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.
- Iron Man [ Watch Video ] [ Download Original Video ]
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.
- Quick PPT [ Download ]
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 [ Go to Site ]
- Original Potato Power Writeup [ Download ]
- Summary of Potato Power portions used [ Download ]
Introduction of AC - Lecture
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 [ Go to Site ] Website with good visual of AC power generation
Student Response Remotes- Polling - Assessment
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.
Power Wars: AC vs. DC - Assessment
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 [ Go to Site ]
- Questions [ Download ]
Additional Resource - Other
The following site offers a multimedia demonstration of "The Energy Grid" that may be used to enrich this lesson or fill remaining time gaps.
- The Energy Grid [ Go to Site ]

Assessment

Assessment Types:: Projects, Writing Samples,

Students will be assessed by their ability to complete a functional DC circuit and their responses to the writing samples and associated questions. Given their performance, looping back will be completed as necessary.