PHYS-224 Test #1 (Chapters 25,26,27)
Things to remember:
- Anything we did in class is fair game - whether I did it as an example on the board, or you did it in the workbook.
- Anything from the Mastering Physics homework is fair game.
- Problems you are asked to solve may not look exactly like examples from class or homework, but will involve exactly the same processes or concepts. Don't just memorize examples, make sure you understand the physics concepts and the reasons behind the solutions.
- You MUST show all work or provide an explanation in order to receive full/partial credit. This includes multiple choice questions.
Things you should be able to do
- Explain how you could experimentally determine whether or not an object was charged and what type of charge it carries.
(see student handbook pg. 25-1,2 #4,5 and pg. 25-4 #11)
- Calculate how many fundamental units (e) of charge an object carries
- Explain the differences between a conductor and insulator regarding charge motion, the distribution of net charge, and electric fields within the material
- Identify which charge is the source and which is the test object
- Draw and calculate the unit vector pointing from source to test object
- Draw and calculate the vector force between two points charges
(see student handbook pg. 25-9 #22,23,24)
- Given two point charges, determine the location where a third charge would experience zero net force.
(see student handbook pg. 25-10 #25,26 and pg. 26-1 #6)
- Draw and calculate the electric field vector at a location due to one or more point charges
(see student handbook pg. 25-11 #31 and pg. 26-2,3 #5,7,8 also pg. 26-5 #16,17)
- Predict (concept) what will happen to a charge which has an initial velocity and enters a region with a uniform electric field
(see student handbook pg. 26-11 #33,34,35)
- Calculate the acceleration experienced by a charge moving in through an electric field and use the equations of motion to calculate where it will hit, how far it will go, etc.
- Determine the total charge if given charge density and dimensions
(see student handbook pg. 26-7 #24)
- Setup (and possibly solve) the integral process for finding the electric field for a line-type charge
- Determine whether or not an electric field matches the symmetry of a charge distribution
(see student handbook pg. 27-1 #1)
- Calculate the flux through a surface (given E, A, and angle)
(see also student handbook pg. 27-2,3 #3,4,5,6,7)
- Calculate the net flux through a closed surface
(see student handbook pg. 27-4through 27-8 #10,11,13,14,16,17,18)
- Use Gauss's law to determine the distribution of charge on a hollow conducting shell
(see student handbook pg. 27-9 #22,23)
- Be able to explain how correctly picking a surface to match symmetry simplifies the nasty integral in Gauss' law.
- Apply Gauss' law to find E for spherical and cylinderical geometries (solids, shells, insulators and conductors and combinations)
Practice Test
Here's a copy of the test I gave my PHYS-224 students in Spring 2007 term. I am providing this only to give you an idea of the difficulty level you might expect to see. Please don't expect your test to look exactly like this example. Remember: the correct way to use this practice test is to actually take it as a practice test. In otherwords, AFTER you have spent some time reviewing and practicing the things you need to know, find a quiet location (cubicle desk in the library) and give yourself one hour to try to work the test using only the equation sheet, a pen/pencil and calculator. Use your performance to help you figure out what you need to spend more time studying, or to help you manage your test taking time and anxiety better. There is no guarantee that your test on Monday will contain the same questions this practice test. Your questions may be considerably different - (anything on the list above is fair game) - but they will be of similar difficulty..
I will admit that a frequent student complaint about my tests is that students think they are long. I make sure that I can write out the entire solution to the test showing all work in about 15 minutes. If you are not prepared to take the test - that is, if you are still struggling to remember what the electric field for a point charge looks like, or what charge density is, or why the electric field in a conductor is zero, then you will end up wasting a lot of precious time on this test. If you know what you are doing, my tests are very doable. If you have not taken the time to develop the skills and to practice working problems quickly, then you will find my tests to be long. Part of "knowing the material" is being able to quickly recognize what to do with a problem.
Here's a the answers --- but don't look at these until after you have worked the practice test.