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Mikhail and Grant Valerie and Evan Kevin and Rebecca Ally and Katherine Matt M. and Joe Sebek Morgan and Quanbiao Laura and Charlie Lauren and Lu Mikey O. and Ashkan Hannah and Naichen Jim and Dale Nick and Disha Ben and Efrain Nik and Da. Please sit together in pairs:
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Mikhail and Grant • Valerie and Evan • Kevin and Rebecca • Ally and Katherine • Matt M. and Joe Sebek • Morgan and Quanbiao • Laura and Charlie • Lauren and Lu • Mikey O. and Ashkan • Hannah and Naichen • Jim and Dale • Nick and Disha • Ben and Efrain • Nik and Da • Please sit together in pairs: • Mike A. and Heran • Barney and Joe Serruto • Thomas and Yiran • Glenn and Steve T. • Ann and Joey B. • Johnny and Andrea • Korey and Stephen H. • Will and Qihan • Michael W. and Nicole • Zach and Ed • Casey and Zhenmin • Audrey and Taehoon • Lisette and Shenheng • Erica and Matt R. Phys 150 Lecture 12
Announcements • Exam 1 solutions available online. • Homework 6 is due on Monday, Oct. 15 at midnight. Phys 150 Lecture 12
Power Bulbs • 100 Watt incandescent light bulb • Most of the power is producing heat, not light • 26 Watt Compact Fluorescent Light (CFL) • Same light output with ¼ the energy use! • Light Emitting Diode (LED) • About same energy efficiency as CFL Phys 150 Lecture 12
Chapter 6 – Electricity and Magnetism • Electricity Van de Graaff Water Phys 150 Lecture 12
i>clicker question Chemical reactions produce voltages that are typically • 1 volt • 100 volts • 10,000 volts • 1 million volts Phys 150 Lecture 12
i>clicker question Chemical reactions produce voltages that are typically • 1 volt = 1 eV per electron • 100 volts • 10,000 volts • 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 Phys 150 Lecture 12
i>clicker question When you get an electric shock from a door knob, the voltage is typically • 1 volt • 100 volts • 10,000 volts • 1 million volts Phys 150 Lecture 12
i>clicker question When you get an electric shock from a door knob, the voltage is typically • 1 volt • 100 volts • 10,000 volts – actually, more like 50,000 volts • 1 million volts • Sparks - 30,000 volts/cm (in air) • A spark is an electric current in air Wimshurst Phys 150 Lecture 12
i>clicker question Resistance model The resistance of a conductor • increases with increasing temperature • decreases with increasing temperature • is independent of temperature • It depends on the material Phys 150 Lecture 12
i>clicker question The resistance of a conductor • increases with increasing temperature • decreases with increasing temperature • is independent of temperature • It depends on the material Platinum Semiconductor Phys 150 Lecture 12
i>clicker question The voltage from an electrical outlet is • a constant 110 volts • a constant 220 volts • varying (average 110 volts) • varying (average 220 volts) Phys 150 Lecture 12
i>clicker question The voltage from an electrical outlet is • a constant 110 volts • a constant 220 volts • varying (average 110 volts) • varying (average 220 volts) – Europe (50 Hz) • Varies 60 times/sec (60 Hz) • Alternating current (AC) vs Direct current (DC) Light string Phys 150 Lecture 12
i>clicker question We use AC for electric power distribution because • it makes it easy to change voltage • it is less dangerous • most devices require AC current • it is cheaper Phys 150 Lecture 12
i>clicker question We use AC for electric power distribution because • it makes it easy to change voltage • it is less dangerous • most devices require AC current • it is cheaper • High voltage -> Low current (P=IV) • Low current -> Less power loss to heat (I2R) Power lines Fuse Phys 150 Lecture 12
i>clicker question An electric spark of 50,000 volts may not hurt you if • the current is low • the current lasts a very short time • the power is low • Any of the above Phys 150 Lecture 12
i>clicker question An electric spark of 50,000 volts may not hurt you if • the current is low • the current lasts a very short time • the power is low • Any of the above • P = IV • Energy = P x time Phys 150 Lecture 12