Course Info » Course Goals
For specific chapter by chapter content goals (useful at exam time!) see below.
(For some general comments on preparation for this course, see the bottom of the page )
Course Goals
What we cover and why:
Physics 2020 is the second semester of an algebra-based sequence in college physics. We emphasize conceptual understanding and problem solving skills. We will cover topics in modern physics, including electricity, magnetism, light, optics, and more: the foundations of our technological society. Our goals are for you to continue developing knowledge and intuition about how the world works, to learn to approach physics problems on both qualitative and quantitative levels, to relate classroom physics to the real world you live in, and to develop a deeper appreciation of the scientific method. We want you to learn to understand everyday phenomena of electricity and magnetism in terms of just a few basic and understandable physical laws.
This material largely involves discoveries less than 150 years old. (Of course, even the ancients knew some things about magnetism and light). We are so comfortable with technologies like TV and computers, it's easy to forget just how recent these developments are: some of you may have relatives old enough to remember the days before radio (the first licensed broadcast station opened in 1920). We live radically more convenient and perhaps longer and more enjoyable lives due to the revolution in electricity-based technology. Modern health-care, industrial, and home tools are based on the existence of electrical power and electronics. By the end of this course, you should have a base of knowledge to allow you to better understand how many modern electronic devices work.
Specific content goals, organized by chapters:
Let us know if you don't understand what any of these goals are referring to, or if you think we left out a really important idea so I can fill it in!)
Math Background
Students should be able to...
... use trigonometry to relate the sides to angles of right triangles
... use algebra to solve basic equations (including the quadratic equation) for an unknown
... use algebra to solve two linear equations in two unknowns.
Phys 2010 material:
... properly draw a force diagram. This includes being able to identify forces, label them, get the direction correct for "normal force", "friction force", gravitational force, spring force, and "tension force".
... identify "Newton's 3rd law force partners", and recognize when forces are equal/opposite as a result of Newton's 3rd law.
... know and use the formulas for spring force (-kx), kinetic friction (mu * normal), gravity near earth (mg) and gravity far from an object (GM1 M2/r^2)
... use a force diagram, along with Newton's 2nd law, to come up with an equation (or set of equations)
... recognize when a problem is best solved by {kinematics equations, Newton's 2nd law, and/or conservation laws}
... state and use the principles of {conservation of momentum, conservation of energy, and/or Newton's second law} to solve basic word problems involving pointlike objects moving under the influence of simple forces
... know and use the formulas for kinetic energy (1/2 m v^2) and potential energy for gravity near earth (mg*height), for springs (1/2 k x^2), and for gravity far from a massive object (-G M / r)
___________
And now the new stuff:
Chapter 16: Electric Charge and Electric Fields
Students should be able to...
... qualitatively describe forces of like and unlike (pointlike) charged objects in arbitrary configurations
... use the principle of conservation of electric charge and symmetry considerations to solve problems in which charges get re-distributed.
... define the terms "conductor" and "insulator", and recognize that e.g. metals are conductors, plastic or rubber is insulator (etc) without being told
... describe the process of "charging by induction", in pictures and words
... use arguments about movement of charges to describe behaviour of objects in the presence of charges. This includes being able to use sketches to justify explanations (e.g. with electroscope leaves)
... use Coulomb's law to compute forces between charges, and use vector addition (the "principle of superposition") to compute vector forces in systems with more than just two charges. (This includes knowing the SI units of charge, force, and the constant "k" in Coulomb's law)
... know the definition of Electric field, be able to relate it to "electric force" (and vice-versa), and compute electric field in any situation involving a small number of point charges. Related to this - you should know what we mean when we say "test charge" (e.g., it is small, it does not change or impact a given electric field, it is used to measure E-fields)
... draw sketches of electric fields in 2-D (2-dimensional) situations (arising from a small number of point charges),
... interpret drawings of electric fields in 2-D to describe, qualitatively, forces on test charges. There are various representations used to show electric-fields, students should be able to interpret any of the ones we use commonly in class, in the text, or in PhET simulations.
... state the "rules" for electric fields in the presence of conductors, be able to explain why these rules are true, and use those rules to draw basic conclusions about forces on test charges in the presence of other charges and conductors. (These rules include: "E=0 inside conductors in static equlibrium", and "E-fields are perpendicular to surfaces of conductors on the outside", "E-field lines do not cross one another", "E-field lines start and stop only on charges, in static situations".)
Note: We will not cover "Gauss' law" explicitly - it will not be required on our tests.
Chapter 17: Electric Potential
Students should be able to...
...Compute work done by a force (including getting the signs right), and use the work energy theorem which says W_net = change in kinetic energy
... Compute potential energy (PE, or "U") for particles in a force field (like uniform gravity, uniform E-field, or near a point charge or set of point charges)
... Relate Voltage to PE, using V = PE/q
... Connect voltage with E field, through the relation V = - Ed (for uniform fields)
... Interpret "equipotential" diagrams, which includes: relating them to Electric field diagrams (knowing the rules for how E field lines are perpendicular to equipotentials, and how the spacing of equipotentials lines determines the strength of the field)
Also, you should be able to use an equipotential diagram to predict or explain motion of charged particles (of either sign!) and also use it to figure out the work done moving a charge around such a diagram.
... Know the differences between "W_external", "W_net", and "W_field", and be able to calculate any of these in problems like the one just described above: with charges moving around an equipotential diagram (or, near a given distribution of point charges)
... Use and convert between SI metric units (Joules) and eV (electron volts), and know the metric units of all our commonly used quantities (like voltage, potential energy, E-field, etc)
... Use and interpret the formula V = kQ/r, including: knowing when it holds, being able to interpret the sign, use it to compute potential energy of particles near charges, and "superpose" voltages when there are multiple point charge
(The next goals are still Ch. 17, but will be tested on Exam 2, not Exam 1)
... Relate Capacitance, voltage, and charge, and be able to compute the capacitance of a simple "parallel plate capacitor" knowing the dimensions.
... Be able to choose and use appropriate formulas to make qualitative decisions about what happens to the stored energy, charge, E field, capacitance, or voltage across a capacitor as changes are made (e.g. moving the plates apart, changing the plate area, etc.) when it is either isolated, and/or when it is connected to a battery.
Chapter 18: Electric currents
Students should be able to...
... Recognize and draw "circuit diagrams", using our usual notation and conventions (for batteries, resistors, ideal wires, and capacitors) This includes being able to mentally "transform" a diagram (e.g. realizing that wires can be bent or stretched) and translate back and forth from "real world" circuit pictures to our idealized diagrams.
... Know that a battery is a source of fixed potential difference (NOT some "fixed current"!)
... Clearly distinguish between "Voltage across" and "current through" circuit elements
... Understand and use the "Current rule" (which we often state as "total sum of current in = total sum of current out") This means being able to deduce the mathematical relationship between currents entering and exiting a "node" in any diagram, and also knowing and using the fact that if there are no nodes in some part of a circuit, that the current must be the same everywhere along that part of the circuit.
... Know the definition and units of current, including being able to determine the direction of a current when some of the charges involved are negative (so the current goes "the other way" from the motion of the negatives)
... Use Ohm's law to relate Voltage drops, current, and resistance in a variety of problems including simple circuits or "standalone" parts of circuits. This includes knowing SI units, and deciding what the appropriate "Delta V" is (the difference across a resistor)
... Relate resistance (a property of some object) to resistivity (an intrinsic property of some material), length, and cross sectional area, and use this both quantitatively and qualitatively to describe resistance and resulting current flow in simple circuits.
... Know the formulas (and SI units) for power (rate of energy transformation) for circuit elements, and be able to use this formula to make qualitative decisions about what happens to the power dissipated as various changes are made (to resistance, current, or voltage) depending on what is known or held fixed.
... Know what a fuse is, recognize its symbol in a circuit diagram, and be able to decide its effect on a circuit.
... Qualitatively recognize the difference between "DC" (Direct current) and "AC" (alternating current) - i.e. treating AC circuits "on average" by using the same formulas and results from earlier in Chapter 18 (Ohm's law and the "power" relations.)
... Be able to interpret an oscilloscope trace of an AC signal and determine frequency, period, and amplitude.
NOTE: We will NOT require you to compute or work with "RMS" voltage or current, NOR do you need to be able to relate RMS to "peak". This means you don't need material on my notes Ch 18 pp.14-16.
The last parts of Chapter 18 (Microscopic view of current, Superconductivity, human nervous system) are interesting and will help you understand the rest of the chapter, but will not be explicitly tested in any exam question)
Chapter 19: Electric circuits
Students should be able to...
... Use the symbol "EMF" interchangably with "Voltage" of a battery
... Compute "effective resistance" of resistor networks, including series and parallel elements
... use the method of "effective resistance" to solve circuits (which means figuring out current through, and voltage across, and power dissipated by, elements or combinations of elements, in simple resistor/battery networks)
... analyze simple circuits with more than one battery, using intuitive arguments for simple circuits, and using "Kirchhoff's rules" for slightly more complex circuits. Expect to see circuits with one (or two) batteries and between 1 and 4 resistors, with switches or fuses, and be ready to make decisions regarding what happens, qualitatively (brighter or dimmer) or quantitatively (power or current or Delta V) to all the resistors and bulbs.
... apply our rules and formalism to make basic arguments and decisions about safety issues (e.g. knowing what "ground" means, and evaluating what sort of current will flow when touching certain parts of a given circuit)
... know the difference between an ammeter and voltmeter, including how they need to be "wired in" to a circuit to function properly, deduce what will go wrong if they are NOT wired in properly, recognize (or draw) their symbolic representation in a circuit diagram, "solve" circuits that have these meters included.
NOTE: you are NOT responsible for circuit networks that contain capacitors
Chapter 20: Magnetic fields
Students should be able to...
... qualitatively describe forces between simple bar magnets (or compass needles) in simple arrangments
... relate magnetic field to "Force on moving charges" or "Force on wires", properly using the appropriate right hand rule to find the direction, and using the basic formulas (ILBsin(theta) or qvBsin(theta) to compute forces. Students should know what (theta) means in these formulas, and figure it out from a picture)
... draw sketches of magnetic fields arising from a small number of bar magnets or long wires.
... interpret drawings of magnetic fields to describe, qualitatively, forces on test "compass needles". There are various representations used to show magnetic-fields, students should be able to interpret any of the ones we use commonly in class, in the text, or in PhET simulations.
... use "superposition" of B field vectors to relate the TOTAL B field to the B field arising from separate magnets.
... know the qualitative story of charged particles moving in circular orbits as a result of B-fields, correctly determining the direction and qualitative features (relating radius, charge, B field, velocity or momemtum)
... know and use the formula for the B-field from an infinitely long straight wire, including its direction, and be able to "superpose" B fields from multiple sources. Know the SI units of the magnetic field. (The constant "mu_0" will be given on our crib sheet)
(THIS is the stopping point for Exam 2 this year - the material below will appear on the 3rd midterm)
... be able to compute the force per unit length between two long parallel (or anti-parallel) currents (magnitude and direction)
... make qualitative determination of the direction of torque on a loop of current in a magnetic field
... be able to derive and use the "velocity selector" formula v = E/B (when does it apply, what does it tell you, what is the configuration of E and B fields that makes this work?)
... use the basic ideas of magnetic force, and Faraday's law, to qualitatively describe the motion of a motor, or the current resulting from a generator.
We did not cover section 20.8 . We covered 20.9 only qualitatively, no "torque" formulas required. 20.10 is applied examples of 20.9 . 20.11 reviews the physics of circular motion in a B-field (and velocity selector) from earlier. We talked very qualitatively about 20-12, but I don't need you to memorize this terminology.
Chapter 21: Electromagnetic induction and Faraday's law
Students should be able to...
... know and use the definition of magnetic flux to compute the flux given B-field, and an area. This includes understanding which angle is "theta" in the formula Flux = B*A*cos(theta)
... use Faraday's formula to compute and relate EMF, number of turn, and the rate of change of magnetic flux through a loop. (This includes being able to figure out "rate of change" when the flux is a LINEAR function of time)
... Use and apply Lenz' law (the minus sign in Faraday's law) to correctly predict the direction of flow of induced current in a loop in a variety of situations where magnetic flux is changing (including recognizing when the flux is NOT changing, and thus no induced currents appear). This also iincludes situations we refer to as "eddy currents" - being able to deduce the direction of flow of the eddy current given a typical situation of metal moving relative to a magnetic field
... apply Faraday's law to situations of "moving rails" to compute EMF, direction of current flow, and the magnitude of the current
... Connect back to the previous chapter to predict the direction of the force on an induced current, in the presence of a magnetic field.
... know and use the "transformer formula" VS/VP = NS/NP, including being able to identify what "secondary" and "Primary" refer to in a given pictorial setup, knowing when the formula does NOT apply (e.g. steady voltages), and knowing the terminology "step-up" and "step-down" transformers
... be able to use conservation of energy (power in = power out) to also deduce the ratio of CURRENTS (not just voltages) on both sides of a transformer.
We talked about the examples in 21.8, but I don't need you memorizing this stuff, it's just further examples. We did not cover Chapter 21.9 to 21.14 at all.
Chapter 22: Electromagnetic waves
Students should be able to...
... use the basic terminology associated with traveling waves, including knowing and identifying wavelength, frequency, period, wave speed, "spectrum".
... apply the basic relation wavelength * frequency = speed, and know that the speed of all traveling EM waves in vacuum is c = 3E8 m/s.
... relate period to frequency (T = 1/f)
... know the units of "intensity" = joules/(area*time), and use that to answer basic questions relating power, energy, and intensity.
We did not cover the rest of Chapter 22.5, or 22.6-7 in any detail.
This is as far as Exam 3 will take us! The rest will be on the final - (which is also cumulative!)
Chapter 23: Geometric Optics
Students should be able to...
... distinguish specular and diffuse reflection
... draw and/or interpret simple ray diagrams involving flat planar mirrors, including identifying "incident" and "reflected" angles, knowing those are equal, and locating the image in a simple flat mirror. This includes understanding the idea of "parallax" as introduced in lab, to locate an image.
... know the notation we have used (angle of incidence, angle of reflection, angle of refraction, specular vs. diffuse, image and object distance)
(Note: we will not cover Ch 23.3, curved mirrors!)
... know and be able to use Snell's law to solve for lights path through media
... relate index of refraction to speed of light in a medium
... be able to compute "critical angle", and know when it applies and what effects it has (total internal reflection)
... know the difference between real and virtual images
... use the "ray model of light" to visualize and make sense of how light moves, and how it forms images
... be able to draw and interpret ray diagrams for a simple (thin) convex (converging) or diverging lens, including all three principal rays, and be able to connect the pictures to the "thin lens equation" (1/do + 1/di = 1/f) and the magnification formulas (m = hi/ho = -di/do), including getting signs right and making physical sense of results. (is the image upright or inverted, magnified or reduced, real or virtual, etc)
...be able to make qualitative deductions from the above, like what happens to an image when you make changes to the focal length, or object distance, or index of refraction, etc.
... (Ch 25) know the difference between near-sighted and far-sighted eyes, and relate that to ray diagrams and the lens formula
Chapter 24: Physicsal optics
Students should be able to...
... be able to draw and interpret diagrams of light that show its wave nature, like Fig 24.6-8 in your text
... be able to make qualitative conclusions about double slit patterns (what happens to the pattern if you change lambda or frequency? How about d? Or, the distance to the screen?), and quantitative conclusions too (being able to calculate)
... know when you can use the "small angle" approximation sin(theta) = tan(theta) = theta, and use it correctly.
... Know and be able to use the constructive and destructive interference equations, d sin(theta) = m lambda, or (m+1/2), and also understand the derivation/origion of those equations: intensity arises from constructive or destructive interference depending on the phases of the wave.
... qualitatively describe "diffraction"
... correctly predict the rainbow effect (which color gets bent more?) from gratings.
The rest of this page is much more general. Just read it if you are interested!
COURSE SCALE LEARNING GOALS
These are very broad (course scale) goals - content goals are something different ( see above!)
- Math/physics connection: Students should be able to translate a physical description of a physics problem (e.g. a "word problem") to an algebraic equation (or trigonometic relation) necessary to solve it. Similarly, students should be able to explain the physical meaning of the algebra (or trig) associated with our physics problems. Students should be able to achieve physical insight through the mathematics of a problem.
- Visualize the problem: Students should be able to sketch the physical parameters of a problem (e.g., E or B fields, distribution of charges, circuit-diagrams), as appropriate for a particular problem, and recognize and interpret the commonly used visual representations that occur in this course. Many topics in this course have multiple-representations (e.g., we might draw an E-field with a bunch of arrows on a grid of points where the length of the arrow represents field strength (or perhaps the darkness/brightness of the arrow represents field strength), or as 'field lines' (where the density of the lines on the page represents the field strength) - students should be familiar with these multiple-representations, and make use of them to solve problems.
- Organized knowledge: Students should be able to articulate the big ideas from each chapter, section, and/or lecture, thus indicating that they have organized their content knowledge. They should be able to filter this knowledge to access the information that they need to apply to a particular physical problem.
- Communication. Students should be able to explain their thinking and/or approach to a problem or physical situation, in either written or oral form.
- Problem-solving techniques: Students should be able to choose and apply the problem-solving technique that is appropriate to a particular problem. This indicates that they have learned the essential features of different problem-solving techniques (eg., breaking vectors into components, methods of adding and subtracting vectors, solving basic algebraic expressions for an unknown, reducing a circuit to a simpler "equivalent circuit", properly using the various "right hand rules" to find directions of forces or fields). They should be able to apply these problem-solving approaches to novel contexts (i.e., to solve problems which do not map directly to those in the book), indicating that they understand the essential features of the technique rather than just the mechanics of its application. They should be able to justify their approach for solving a particular problem.
- Metacognition: Students should be able to justify their choices in problem solving methods verbally or in writing, and explicitly engage in discussion about their thinking and what helped them learn.
- Problem-solving strategy: Students should be able to draw upon an organized set of content knowledg and apply problem-solving techniques (see above) to that knowledge in order to organize and carry out solutions to "word problems". They should be able to connect the pieces of a problem to reach the final solution. They should recognize that wrong turns are valuable in learning the material, be able to recover from their mistakes, and persist in working to the solution even though they don’t necessarily see the path to the solution when they begin the problem. Students should be able to articulate what it is that needs to be solved in a particular problem and know when they have solved it.
- Expecting and checking solution: When appropriate for a given problem, students should be able to articulate their expectations for the solution to a problem, such as direction of the field, behavior at large distances, what happens when a resistor becomes infinite (or shorts out), etc. For all problems, students should be able to justify the reasonableness of a solution they have reached, by methods such as checking the units of their solution, looking at basic limits, relating to cases with known solutions, and/or checking the order of magnitude of the answer.
- Intellectual maturity: Students should accept responsibility for their own learning. They should be aware of what they do and don’t understand about physical phenomena and classes of problem. This is evidenced by asking sophisticated, specific questions; being able to articulate where in a problem they experienced difficulty; and take action to move beyond that difficulty.
- Build on Earlier Material. Students should deepen their understanding of Phys 2010 material. I.e., the course should build on earlier material, including Newton's laws, energy conservation, and appropriate math (including working with vectors, solving basic algebra problems, and using trigonometry when appropriate)
Important comment on preparation:
Physics 2020 is a challenging physics course. Physics 2020 covers much material you likely have not seen before, at a higher level of conceptual and mathematical sophistication than you may have encountered in a physics class so far. Many of the ideas in this course are among the greatest intellectual achievements of humans. Don’t be surprised if you have to think hard and work hard to master the material!
Therefore you should expect:
- a large amount of material covered quickly.
- many problems will be different from examples from class and the text. We want you to learn how to extend what you know to tackle new, fresh problems - this is different from memorizing facts (or "solution methods" that can be applied blindly) This kind of "problem solving" can be unfamiliar and disequilbrating at first, but is one of the most useful outcomes of a physics course!
- hard, sometimes long homework problems. Make use of the helproom, office hours, the piazza page - maybe form a study group.
- challenging exams.
YOU control the pace of the course by asking questions in class. I tend to speak quickly, and questions are important to slow down the lecture. This means that if you don’t understand something, it is your responsibility to ask questions. Attending class and the lab/recitation sessions gives you an opportunity to ask questions. We are here to help you as much as possible, but we need your questions to know what you don’t understand.
Physics 2020 covers some of the most fundamental physics there is. Your reward for the hard work and effort will be learning important and (sometimes) elegant material, and "habits of mind" that will help you in many contexts in your professional and personal life!
Here is what we have experienced:
- This is a 5 credit course. Most students reported spending >10 hours per week outside of class.
- students who don’t attend lectures and helproom often did poorly in the class.
- students reported learning a tremendous amount in this class.