External Knowledge Training

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Physics - Introductory Berkeley course

All notes by John Eagles

1 Introduction

Today i started watching this introductory course in physics. It's a UC Berkeley course given by Richard Muller. He explains physics without using many equations. In this particular lecture he comments quite a bit on 9/11 related physics and dwells on terrorist shoe bombs. He advises the government in such matters, so his views seem a bit politically colored. But he really knows how to present laws of physics in a very understandable and close-to-life manner. I've learned quite some new things from watching this lecture.

2 Solar technology, coal reserves

Summary of topics lectured about:

1. Calories of food
2. Peripheral vision of the eyes detect especially motion
3. Solar technology
4. Tilt of the earth & the seasons
5. Global warming in relation to the forming of clouds. When the climate heats up, more clouds may form and may counter the greenhouse effect.
6. Canada is 2nd in the world after Saudi Arabia for its oil reserves, but Canada has it stored in oil sand and it's more expensive
7. Natural gas & shale gas in comparison to oil
8. Coal reserves: The USA has most reserves, then comes Russia and then China, Australia and India. These reserves are big in terms of energy compared to the world's oil reserves.
9. Coal and methane can turned into gasoline, but it's still risky in case the oil prices are lowered.
10. In politics, there's conflict between the issues of global warming and energy security.
11. Coal is the cheapest form of energy.
12. IPCC errors
13. Sequestering CO2 and making clean use of coal
14. CCS = Carbon Capture & Storage
    

3 Temperature scales

Topics in this video:

1. Size of atoms
2. Density of atoms
3. What makes atoms move, what gives them the kinetic energy?
4. Temperature = how much energy do things have
5. Thermometers
6. Scales of Celcius, Fahrenheit
7. Liquid nitrogen experiments
8. There are ca 1000 x more molecules in a fluid than in a gas of the same substance per volume
9. Temperature of absolute zero on the Kelvin scale means there is no energy
10. In the Kelvin scale the amount of energy is proportional to the temperature
11. A fire extinguisher has liquid CO2
12. Your subjective temperature measurement
13. Hot air rises because it's less dense
14. Conduction, convection, radiation

Lecturer is Bob Jacobsen

4 Thermodynamics intro

1. The ideal gas law (relationship between volume & temperature)
2. Movements of small and bigger molecules and atoms
3. Energy efficiency of engines
4. Refrigerators
5. Air conditioners
6. Entropy = a measure of disorder
   

5 Satellites, gravity

This lecture is about:

1. Friction
2. Movements of satellites
3. Why frisbees and airplane wings lift
4. Satellites move with 5 miles per second. They are falling but because the earth is curved, they fall with the earth curve
5. Rockets escape velocity
6. Gravity force between two people near to each other is ca mass of a mosquito
7. What does it mean to be weightless
8. How do spy satellites work. They have to be close to the ground. It takes them 1 1/2 hour to orbit the earth one time.
9. Unmanned drones
10. Weather and tv satellites orbit the equator at 22000 miles high and need 24 hours for one cycle: Geostationary satellites
11. 24 GPS satellites go around in 12 hours.
    

6 Newton's laws, inertia, circular motion

Topics explained in this lecture, illustrated with several experiments:

1. Newton's laws
2. Inertia
3. Circular motion
   

7 Radiation, radioactivity

• Ionizing radiation knocks electrons off atoms.
• We're exposed to some amount of ionizing radiation all the time.
• Tritium is used in some watches.
• Damaging of DNA is what causes cancer.
• Sieverts - Grays - rems.
• 2500 rems (25 Sieverts) on average causes 1 fatal cancer. It's a probability.
• Radiation illness - requires much less than a dose causing cancer.
• About percentages of increase of cancer because of radioactivity.
• Alpha rays don't penetrate deeply, are stopped by the skin.
• X-rays.
  

8 Global warming, radioactive rays, radiocarbon dating

• Categories of believers and non-believers in global warming.
• Errors in IPCC reports
• He quotes research stating that organic food is unhealthy?!?
• Chemotherapy & radiation therapy against cancer, how does it work?
• The energy release of exploding a nucleus is typically 1 million times more than energy released in chemical reactions.
• In the early universe almost all atoms probably were explosive or radioactive.
• Radiocarbon dating with C14, having a half-life time of 6,000 years. C14 is in the atmosphere because of cosmic radiation affecting C atoms. Living organisms take in a percentage of these C14 atoms. The amount of C14 in the atmosphere is constant.
• Potassium-Argon dating: A dating method using rocks.
• Beta rays are fast electrons.
• Alpha rays consist of small nuclei of 2 protons and 2 neutrons that form He atoms when the rays are stopped.
• Gamma rays are penetrating, not ionizing colliding particles. They pass through things. They knock off electrons and are very energetic.
• X rays are the same as gamma rays but more energetic. X-ray photos create shadows.
  

9 Nuclear reactors, uranium, chain reactions

This lecture is about:

• How to get useful energy from radioactive elements.
• Chain reactions and nuclear fission.
• U235 is more radioactive than U238, but there's much less of U235 on earth (U = uranium).
• Enrichment of uranium is removing what you don't want, for example by using centrifuges.
• Depleted uranium.
• Natural and oldest man-made nuclear reactors.
• The nature of chain reactions.
  

10 Nuclear waste, fusion reactors

• Where to store nuclear waste?
• Safety measures for nuclear plants.
• Spent fuel rods and spent fuel storage installations.
• Nuclear waste transport.
• Waste from uranium mines.
• Fusion reactors are still not commercially operated.
  

11 Graphene, electricity basics

• Four different carbon bonds.
• Graphite and graphene. Graphene is a newly produced one-layer sheet of graphite.
• Sparks from static electricity.
• Voltage, currents, resistance.
• Fuses and circuit breakers.
• Electrocution.
• Fibrillation of the heart.
• AC and DC currents.
  

12 Magnetism

• What is magnetism?
• Rare-earth magnets have transformed society.
• Rare-earth minerals.
• The earth is a magnet.
• Magnetism comes about when there is a moving charge.
• Magnetic recording, hard disks, credit cards.
• Electric generators = moving wires pass a magnet.
• Transformers.
• Voltage is energy per electron.
• Magnetic levitation.
  

13 Scientific implications of magnetism - Electrical power

• Power = voltage x current.
• A moving magnetic field makes voltage and provided there is a conductor, a current.
• Alternating currents and direct currents (AC and DC).
• Edison's first promoting of his electric bulbs.
• High-voltage wires.
• Smart grids.
  

14 Waves

• Seismographs measure the shaking of the ground.
• Atoms are basically a kind of waves, quantum waves.
• A particle is a wave.
• When you shake the vacuum it becomes a wave.
• A wave is moving energy.
• The old concept of 'aether' is now renamed 'vacuum.'
• Different types of waves.
• Earthquakes & tsunamis.

There's a funny interruption of the lecture because of student demonstrations.

15 More about waves

• Waves have three characteristics:
  • Amplitude (height or size)
  • Energy (intensity or power)
  • Speed (small and big waves travel at the same speed)
• Strings of music instruments.
• Piano tuning.
• Interference of sound waves.
• Sound waves.
• Interference of FM radio waves.
• Mirages.
  

16 Mechanical waves

• Mechanical waves transport energy through a medium by elastic deformations.
• Characteristics of mechanical waves:
  • The medium itself has no position, oscillates around a fixed position.
  • Energy is required to create a wave. The wave transports the energy.
  • Waves can transmit information.
  • Waves travel with a fixed speed for a given medium (wave speed).
• A wave pulse is a single propagating disturbance.
• Periodic waves repeat regularly.
• Frequency = cycles per second (Hertz).
• Mechanical waves require a medium (inertia of the medium), and a form of restoring force (pushing the medium back to a starting position).
• Superposition of waves: Bouncing waves don't affect each other in terms of the speed with which they travel and the energy they carry.
• Standing waves form when two identical waves travel in opposite directions.
• Standing waves on guitar strings.
• 1st, 2nd, 3rd harmonics on strings.
  

17 Sound, open and closed pipes

• Sound is longitudinal or compression waves. They can be through any medium with molecules (gas, liquids, solids), not a vacuum.
• Sound is pressure waves, or alternating regions of high and low pressure.
• Speed of sound in air is ca. 340 m/s.
• Air inside a pipe, shock waves inside a pipe.
• The closed end in a pipe always feels the maximum pressure of the wave.
• At the open end of a pipe the molecules are free to move. It's a pressure node, the pressure doesn't change.
• Wind instruments are resonant pipes, open or closed.
• A flute is an open pipe.
• A clarinet is a closed pipe.
• Open pipes have all harmonics.
• Closed pipes have only odd harmonics.
• Beats.
• Doppler effect.
  

18 Electricity

• Electricity is transfer of power or information by electrical forces.
• Electrostatic force: A fundamental force of nature (like gravity).
• Applications:
  • transfer of power
  • storing energy in batteries
  • run appliances
  • light, heat
  • transportation
  • computers, telecommunication, entertainment
• This force comes from electrical charges.
• Electrons have about 1/2000th of the mass of neutrons and protons.
• Electric charges come in two types: Positive and negative.
• Protons and electrons have exactly equal and opposite charges.
• There is a fundamental unit of charge.
• Electrons move much easier than protons.
• Conservation of charge:
  • The universe has no net charge (is what is believed)
  • We cannot create a positive or negative net charge
• The electrostatic force is both attractive and repulsive.
• The gravitational force is only attractive.
• Electrostatic force : gravity = 4 x 10 to the 42 : 1, so the electric force is much stronger.
• Conductors and insulators
• Electrostatic potential energy.
  

18 Electricity

• Voltage = Potential energy / charge.
• Batteries = Chemical charge pump. Chemicals store energy which is converted to voltage.
• Electrical outlets: The ground of an outlet is literally connected to Earth. It is to keep you and the socket at the same voltage.
• Solar cells: Directly convert sunlight into electrostatic charge.
• For a voltage to provide power, a charge must flow. This is an electrical current.
• Negative charges (electrons) flow from negative to positive. The currents flows in the other direction.
• Electrical circuits:
  • Current is usually confined to flow in wires to appliances.
  • No current can flow in an open circuit.
• Electrical power:
  • Voltage = Potential energy / charge
  • Current = Charge transfer / time
  • Power = Voltage x current
• Resistance limits the amount of current flow through a circuit for a given voltage.
• Voltage drop
• Ohm's law: Voltage drop = current x resistance.
• Current = Voltage drop / resistance.
• Power lost = current² x resistance