Physics 213 (welcome!) Instructor: Chris Coffin Wngr 309 coffinc@physics.oregonstate.edu www.physics.oregonstate.edu/~coffinc/COURSES/ph213 4/3/17 Oregon State University PH 213, Class #1

Oregon State University PH 213, Class #1 Announcements ･ For all registration issues, go to the Physics Dept office (Wngr 301). Do not attend any class/lab other than what you are registered for. ･ No labs meet this week. You’ll first meet your lab TA next week; names/schedules will be posted soon. There is a take-home Lab 1 —see the Course Calendar. ･ PH 223 recitations will meet this week. (See also the PH 223 link on the PH 213 home page.) ･ Get your textbook. Use either the full hard-cover or the soft cover/ loose-leaf or the electronic version; all are the 4th edition. The author is Randy Knight; the publisher is Pearson. You don’t need to buy a lab manual—labs will be posted online again this term. ･ We will be using clickers starting this Wednesday. We use the TurningPoint clicker model or the ResponseWare software. 4/3/17 Oregon State University PH 213, Class #1

but the Prep is NOT optional. About This Course Read the web site. Start with the Frequently Asked Questions and go from there. The Prep sets are not handed in for points, but the Prep is NOT optional. Strong suggestion: Stay caught up with the reading and Prep schedule shown on the Course Calendar. Do at least a little of the suggested Prep item as scheduled—then return to do the rest as you’re doing your studying before the exam. 4/3/17 Oregon State University PH 213, Class #1

Oregon State University PH 213, Class #1 This term is challenging. Because we will be dealing with the properties of space itself (properties you can’t see with your eyes), you will need your fullest range of visualization skills, physics unit analysis, and “sense-making” habits. This term is math-intensive. Some of the properties of space are vectors. We can do 2-D analysis on many occasions, but (especially when we get to magnetism), we must do 3-D analysis. You will need to be able to construct integrals. You can look up the analytical solutions to various integral forms, but first you have to do the physics to see what forms you have to work with. 4/3/17 Oregon State University PH 213, Class #1

Like mass, charge is an intrinsic property of matter. Electric Charge Like mass, charge is an intrinsic property of matter. Like mass, charge is conserved. Like mass, charge exerts force. Unlike mass, charge has two types: positive and negative. And whereas mass always attracts other mass, the force exerted between two charges may be either attractive or repulsive, depending on whether the charges are positive or negative. Like charges repel. Opposite charges attract. 4/3/17 Oregon State University PH 213, Class #1

Oregon State University PH 213, Class #1 One very common amount of charge is called e. It is the amount of charge found on an electron (-e) or on a proton (+e). The magnitude of the charge, e, is e = 1.60 x 10-19 C The SI unit of charge is the Coulomb (C). Note that the Coulomb is a base, or fundamental, SI unit. Like length, time and mass, charge can be considered a fundamental dimension in the universe. 4/3/17 Oregon State University PH 213, Class #1

Oregon State University PH 213, Class #1 Electrons are much more easily moved from substance to substance than are protons. Protons are more tightly bound—in the nucleus— of each atom. Thus, electrons are the most common carriers of charge. To give an object a net negative charge, you generally add electrons to it. To give it a net positive charge you generally remove electrons from it. The atoms of some substances release electrons much more easily than others. These are called electrical conductors. (The others are called electrical insulators.) 4/3/17 Oregon State University PH 213, Class #1

Oregon State University PH 213, Class #1 Most objects are electrically neutral unless electrons have been added or removed (by force), in a process called charging. When charging occurs, the extra charge (which is either positive or negative) distributes uniformly over the outside of the object— because all those extra “like” charges are all repelled by one another. This happens very quickly in a conductor, such as metal; much more slowly in an insulator. You can charge an object either through contact or through induction. 4/3/17 Oregon State University PH 213, Class #1

Oregon State University PH 213, Class #1 An electroscope is positively charged by touching it with a positive glass rod. The electroscope leaves spread apart and the glass rod is removed. Then a negatively charged plastic rod is brought close to the top of the electroscope, but it doesn’t touch. What happens to the leaves? The leaves get closer together The leaves spread further apart The leaves don’t move One leaf moves higher, the other lower 4/3/17 Oregon State University PH 213, Class #1

Oregon State University PH 213, Class #1 Three balls are suspended from thin threads. Balls 1 and 2 repel each other and balls 2 and 3 attract each other. From this we can conclude that 1. 1 and 3 carry charges of opposite sign. 2. 1 and 3 carry charges of equal sign. 3. All three carry the charges of the same sign. 4. One of the balls carries no charge. 5. We need to do more experiments to determine the sign of the charges. 4/3/17 Oregon State University PH 213, Class #1