1. Winter wk 1 – Tues.4.Jan.05 Tsunami workshop Earth Part 3: Weather Physics Ch.21: Electric charge Physics Ch.22: Electric fields Energy Systems, EJZ

2. Earth, Part 3: Weather & Climate Weather is powered by Sun (79-82) Low pressure = bad weather, rotates CCW in N Jet stream carries weather across US (p.72-73) Heat, moisture, and wind provide weather energy Temperature drops with altitude (in troposphere): air condenses or freezes, and precipitates (83) Cooling water in air releases heat to surroundings

3. Winds

4. Climate Climate = aggregate weather: averaged over space and time: Temp and Precipitation Depends on Sun, land covers, and longer-term interaction between land, atmosphere, and oceans Recent examples of climate change: 12,000 yrs ago – emergence from ice age Medieval Maximum (1100s) more solar activity, drought in SW ruined Chaco culture Maunder Minimum (late 1600s) few sunspots, frozen N Europe, famine & plague

5. Physics Ch.21: Electric Charge 21-3: Conductors and insulators: Checkpoint 1, #4 21-4: Coulomb’s Law (#2) Compare F electrostatic to F gravity (#65) 21-5: Charge is quantized (#24-26) 21-6: Charge is conserved (#30) Current = rate of flow of charge (lightning #54, defibrillator #56)

6. Charge, conductors, insulators 21-3: Conductors and insulators: Checkpoint 1

7. Coulomb’s law 21-4: Coulomb’s Law (#2) Compare F electrostatic to F gravity (#65) 21-5: Charge is quantized (#24-26) 21-6: Charge is conserved (#30) Is e=e - or e + ? (a) p  n + e  (b) n  p + e 

8. Current = rate of flow of charge Current = rate of flow of charge (defibrillator #56) #54: In the return stroke of a typical lightning bolt, a current of I=2.5 x 10 4 A exists for t=20  s. How much charge is transferred in this event? Current = charge/timeI = Q/t Charge Q =

9. Physics Ch.22: Electric Field 22-3: Electric field E maps the direction and strength of the force F (Q1, #1, 2) 22-4: Field due to a point charge (Q2, 5, #4, 11, ) 22-8: Point charge can be accelerated by an electric field (Q8, #38, 39, 49) Compare to gravity: #75, 85 (42)

10. E field maps electric force 22-3: Electric field E maps the direction and strength of the force F (Q1, #1, 2)

11. Field due to a point charge 22-4: Field due to a point charge (Q2, 5, #4, 11, ) If the Earth’s electric field is 150 N/C near the surface, what is the charge Q on the Earth? What is the charge density (  =Q/area)?

12. 22-8 E field can accelerate charges Q8, #38, 39, 49 Compare E to gravity: #75, 85 (42) A spherical water droplet is suspended in a cloud with E=462 N/C (a) What is F g on the drop? (b) How many excess electrons does it have?