Exam #2 Study Guide:
Exam 2 will have 40 multiple choice questions based on
material covered in lectures 8 to 15. Material from HW #5-7 may be on the exam.
A few of the questions will involve simple calculations, so you should bring
your calculator. You will not need your clicker. You may bring one double-sided
8.5x11 inch sheet of paper with notes to the exam.
I Energy Conservation and Entropy
- Energy is the ability to do work. It is a scalar and is
measured in Joules, J
- Know that energy is a conserved quantity
- Know the types and how to calculate them: Kinetic (energy
of motion, ˝ mv2), Potential (energy of position, mgh)
- Work = force x distance. Work converts energy from one
form to another.
- Be able to use energy conservation to calculate the height
or speed of something (an example is the LONCAPA problem)
- Power is the rate of change of energy: Power = Energy/time
and is measured in Watts
- Be able to convert food energy to J and how to calculate
how many Calories you burn walking up stairs. 1 Calorie = 1 kcal = 4184 J
- Thermal energy is random motion. More motion means higher
temperature.
- Know the second law of thermodynamics – “you can’t get
something for nothing”. More correct: The entropy of a closed system
always increases.
- Entropy
- Is a measure of the number of possible ways to arrange a
system
- The second law says in any process the entropy of a
closed system always increases
- Know how to calculate entropy (two equations)
II Electricity and Magnetism
- Magnetic force: a compass has a north and a south magnetic
pole. North poles are attracted to south poles; like poles repel.
- The Earth is like a big magnet with a south (north)
magnetic pole near its North (South) geographic pole. All the planets and
our Sun have magnetic fields.
- Electric force: like charges repel; opposite charges
attract
- Charge is a property of matter. The fundamental unit is
1.6E-19C. This is the charge on a proton. An electron has a charge of
–1.6E-19C. Note: quarks have fractional charge, but they are never
observed free in nature.
- Be able to calculate how many electrons are or (or are
missing from) an object.
- What happens to the size of the electric force if the
distance is 2x greater; 3x greater; 10x greater?
- Know that moving charge is the origin of magnetic fields.
- Electric fields
- A vector measured in N/C or V/m
- Charge creates an electric field
- The direction of the field gives the direction of a
forced on a + charge
- Force on a charge q: F = q E (E is made by another
charge Q) [E=F/q]
- Electric Potential; V (which is measured in volts = J/C)
- Be able to find E from V: E = -DV/Dx. Electric
field is the rate of change of electric potential with distance.
- Positive charge makes positive potential
- We can think of potential as hills and valleys. Positive
charge rolls downhill negative charge rolls uphill.
- Be able to look at a graph of potential versus distance
and tell the direction of forces, size and dire
- Circuits
- A battery is like a pump that raises charge up an amount
V and the charge flows around the circuit.
- Current is the rate of flow of charge I = Q/Dt
- As charge flows in a wire heat is generated. This is how
light bulbs produce light.
- Electric materials: Know the 4 types and their
characteristics (conductor, insulator, semiconductor, superconductor)
III Quantum Mechanics Basics
- Electromagnetic spectrum (Radio, microwave, infrared,
visible, ultraviolet, X-rays, g-rays)
- We see photons from 1.8 to 3.1 eV ( energy=hv; v is the
frequency, h is plank’s constant)
- Know period, frequency, wavelength and the relation
c=wavelength x frequency
- Inverse square law and how it explains the r2
dependence of the Coulomb force.
- Know that all objects in nature have particle and wave
properties.
- Know that particles have a wavelength l=h/p. Be able to calculate a
wavelength.
- All particles have a wave nature. The thing that is waving
is probability.
- Waves can overlap, this is called interference.
- Uncertainty principle and be able to use it. Know both the
DxDp
and DEDt versions.
IV The 4 forces of nature
- Know the four forces and their characteristics from the
table in lecture 15
- Be able to recognize simple Feynman Diagrams
- Two electrons, or protons, or other charges objects
interacting via the Coulomb force
- A neutron (actually a down quark in the neutron) decaying
to a proton (an up quark in the proton) by the weak force
- Two protons (or a proton and an neutron, or two quarks)
interacting by the strong force
- Be able to check reactions for Baryon conservation, lepton
conservation, electric charge conservation (review the LONCAPA problem)
- Know what the following words means: Field theory (the
picture where a property of matter creates a surrounding field, like the
electric field from an electric charge), Quantum Electrodynamics (the
field theory for the electromagnetic and weak forces), Quantum
Chromodynamics (the field theory for the strong force)
- Know that Gravity is much weaker than the other forces and
does not seem to fit in.
- Know that neutrinos interact by the Weak force, have mass,
no charge, have lepton number, but don’t interact much.
- Antiparticles have opposite charge, baryon number, lepton
number. When antiparticles meet with their like particle they annihilate
giving off energy.
- Review the contents of the table of particles for lecture
15