Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric charge Forces between charged objects Chapter 20 (Week 1 Day 1) Electric Forces and Fields Topics: Slide 20-1

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Keep in mind Physics is hard but doable Anyone can do physics if they make the effort Many students in pre-medical majors find this the hardest undergraduate class – don’t be surprised if this class is challenging for you Physics is relevant Much of biology uses physics concepts Problem Solving and Thinking skills developed helpful in other areas This class will need a lot of time – be efficient use problem solving sessions and office hours as study time Slide 20-3

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Briefly Go over Class Syllabus Goals Understand and learn how to use the key concepts and equations to analyze a wide range of physical situations Learn to work comfortably with doing algebra in symbols Learn to apply math to physical situations Problem solving emphasis is more on good solutions and reasoning than answers Good Solution and Reasoning 50-90% Correct Answer 50-10% On Quantitative Problems Correct Answer 10-30% credit Slide 20-3

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Briefly Go over Class Syllabus Homework Readings Warm-ups (Either on Paper or on Mastering Physics) - 4% Paper Homework (Conceptual Worksheets + Solutions) - 7% Mastering Physics (Web-based homework system) - 14% Exams 3 midterm exams (will drop lowest) - 2 x 20% Final Exam - 30% Class Participation Clicker Questions + In-class activities - 5% Slide 20-3

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Class Syllabus Questions Exams No notes One page of notes Problem Solving and Office Hours Monday before or after class Wednesday before or after class Thursday 6:30-7:20 PM Earlier Slide 20-3

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Learning about the X-force Slide 20-3

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric Charges and Forces, Part I Slide 20-8

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric Charges and Forces, Part II Slide 20-9

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Building an X-force (charge) detector Slide 20-3 Construct an electroscope that can be used to test for the presence of charge, as shown and described below. Soda Can Narrow Aluminum Foil Strip Foam Cup Tape Tape a soda can to an inverted foam cup. Bend the can opening so it sticks out of the can. Cut a small 6 cm x 0.5 cm strip of aluminum foil, bend it over a pencil tip, and hook it over the can opening

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Creating top and bottom tapes 1.Take a 10 cm piece of transparent tape and make a handle on the end by folding under the first cm of tape, sticky side to sticky side. Place this tape on the lab table. This is the base tape. 2.Attach a second similarly prepared strip of tape onto the base tape. Label the tape’s handle “B” for bottom. 3.Attach a third similarly prepared strip of tape onto the base tape. Label the tape’s handle “T” for top. 4.Pull the T and B tapes up together as one object. Use your charge detector to determine if this T/B tape is “charged.” Stroke the tapes with your fingers until the charge detector does not respond to the T/B tape. Then pull the tapes apart. You are now ready to start the charged tape homework activity