Amazingly Tempting Future Exam Question: If someone were to walk up to you and ask for a “lay- person’s” explanation of electric current (what we mean by that word, and how it works), what would you say? 4/29/161Oregon State University PH 213, Class #15

Why does the light in a room come on instantly when you flip a switch several meters away? A.Electrons travel at the speed of light through the wire. B.Because the wire between the switch and the bulb is already full of electrons, a flow of electrons from the switch into the wire immediately causes electrons to flow from the other end of the wire into the light bulb. C.The switch sends a radio signal which is received by a receiver in the light which tells it to turn on. D.Optical fibers connect the switch with the light, so the signal travels from switch to the light at the speed of light in an optical fiber. 4/29/162Oregon State University PH 213, Class #15

Another Pretty Good Future Exam Question: If someone were to walk up to you and ask for a “lay- person’s” explanation of electrical resistance (what we mean by that word, and how it works), what would you say? 4/29/163Oregon State University PH 213, Class #15

In lab this week, which factor did you not test for its effect on the electrical resistance of the paper? If there was more than one, choose the one you think would have been most interesting. A.The kind of paper (its material). B.The length of the paper. C.The width of the paper. D.The thickness of the paper. E.The density of the paper. F.The temperature of the paper. G.The moisture content of the paper. H.“We tested all of the above.” I.“I haven’t yet had lab this week, but golly, I’ve sure been thinking about this.” 4/29/164Oregon State University PH 213, Class #15

Figure 30.8A 4/29/165Oregon State University PH 213, Class #15

Figure 30.8B 4/29/166Oregon State University PH 213, Class #15

What happens IN the wire? Voltage means there is an electric field Electric field means charges feel force Free charges in conductors can move: CURRENT! 4/29/167Oregon State University PH 213, Class #15

Figure /29/168Oregon State University PH 213, Class #15

Figure /29/169Oregon State University PH 213, Class #15

Figure Chapter Preview /29/1610Oregon State University PH 213, Class #15

Figure /29/1611Oregon State University PH 213, Class #15

Figure /29/1612Oregon State University PH 213, Class #15

A working model of current and resistance: Put the pieces together 4/29/1613Oregon State University PH 213, Class #15

Figure /29/1614Oregon State University PH 213, Class #15

Figure /29/1615Oregon State University PH 213, Class #15

Figure 30.20A 4/29/1616Oregon State University PH 213, Class #15

Figure 30.20B 4/29/1617Oregon State University PH 213, Class #15