1. Phys 150 Lecture 71 Please sit together in pairs: –Onyema and John W. –Alejandra and Dian –Chris and Michael –Ryan and Honglu –John F. and Matt –Walter and Lin –Max and Anwen –Amanda and Mengyue –Pauline and Melissa –Jennifer and Erich –Alexandra and Irfan –David and Jason –Abigael and Jiayuan –Jake and Erica

2. Phys 150 Lecture 122 Announcements Exam 1 solutions available online. Homework 7 is due on Sunday, March 10 at midnight.

3. Phys 150 Lecture 123 Chapter 6 – Electricity and Magnetism Electricity Van de Graaff

4. Phys 150 Lecture 124 i>clicker question Chemical reactions produce voltages that are typically A.1 volt B.100 volts C.10,000 volts D.1 million volts

5. Phys 150 Lecture 125 i>clicker question Chemical reactions produce voltages that are typically A.1 volt = 1 eV per electron B.100 volts C.10,000 volts D.1 million volts -Alkaline battery = 1.5 volts -9 volt battery = 6 alkaline batteries -Car battery (Lead – Acid) = 6 2-volt batteries -Lithium ion battery = 3.6 volts -NiMH battery = 1.2 volts Lemon

6. Phys 150 Lecture 126 i>clicker question When you get an electric shock from a door knob, the voltage is typically A.1 volt B.100 volts C.10,000 volts D.1 million volts

7. Phys 150 Lecture 127 i>clicker question When you get an electric shock from a door knob, the voltage is typically A.1 volt B.100 volts C.10,000 volts – actually, more like 50,000 volts D.1 million volts -Sparks - 30,000 volts/cm (in air) -A spark is an electric current in air Wimshurst

8. Phys 150 Lecture 128 i>clicker question The voltage from an electrical outlet is A.a constant 110 volts B.a constant 220 volts C.varying (average 110 volts) D.varying (average 220 volts)

9. Phys 150 Lecture 129 i>clicker question The voltage from an electrical outlet is A.a constant 110 volts B.a constant 220 volts C.varying (average 110 volts) D.varying (average 220 volts) – Europe (50 Hz) -Varies 60 times/sec (60 Hz) -Alternating current (AC) vs Direct current (DC) Light string

10. Phys 150 Lecture 1210 i>clicker question The current through a 10 W LED bulb is about A.0.1 Amps B.1 Amp C.10 Amps D.100 Amps

11. Phys 150 Lecture 1211 i>clicker question The current through a 10 W LED bulb is about A.0.1 Amps B.1 Amp C.10 Amps D.100 Amps P = IV 10 W = I x 110 Volts  I = 0.1 Amps

12. Phys 150 Lecture 1212 i>clicker question We use AC for electric power distribution because A.it makes it easy to change voltage B.it is less dangerous C.most devices require AC current D.it is cheaper

13. Phys 150 Lecture 1213 i>clicker question We use AC for electric power distribution because A.it makes it easy to change voltage B.it is less dangerous C.most devices require AC current D.it is cheaper -High voltage -> Low current (P=IV) -Low current -> Less power loss to heat (I 2 R) Power lines Fuse

14. Phys 150 Lecture 1214 i>clicker question An electric spark of 50,000 volts may not hurt you if A.the current is low B.the current lasts a very short time C.the power is low D.Any of the above

15. Phys 150 Lecture 1215 i>clicker question An electric spark of 50,000 volts may not hurt you if A.the current is low B.the current lasts a very short time C.the power is low D.Any of the above -P = IV -Energy = P x time