You are watching: A current carrying wire is wrapped around cardboard tube as shown below.

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Music Who is the Artist? A) B) C) D) E) Oscar Peterson Kenny Barron Dave Brubeck Thelonius Monk Marcus Roberts A classic for a classic day Physics 212 Lecture 17


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Your Comments “Pretty neat stuff. I like how similar this is to Gauss’s law. ” “Need more explanation on the magnetic field directions. ” Easier method to calculate magnetic fields “You should probably look at getting some of the images up and running properly, its hard to deduce anything unless I try to imagine what youre asking about, which in any case i would be right all the time. ” “I find this kind of confusing. Also most of the checkpoint pictures didn’t work for me, so I can’t go back and study from them. It makes it more confusing when I can’t see the pictures to answer questions. . ” “Integrals are my greatest enemy ” Sorry! We’ll go through the checkpoints (with pictures) Spend some time building the integrals “Daaag man, my boy Gauss be gettin’ his style cramped by dat Ampere clown. ” Hour Exam II – THURSDAY Mar. 29 05 Physics 212 Lecture 15, Slide 3


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Infinite current-carrying wire LHS: RHS: General Case : 05 Physics 212 Lecture 15, Slide 4


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Ampere’s Law dl B B dl : 16 Physics 212 Lecture 15, Slide 9


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Ampere’s Law dl B B dl : 16 Physics 212 Lecture 15, Slide 10


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: 19 Physics 212 Lecture 15, Slide 12


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: 19 Physics 212 Lecture 15, Slide 13


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: 19 Physics 212 Lecture 15, Slide 14


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Match the other two: A : 21 B Physics 212 Lecture 15, Slide 15


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A current carrying wire is wrapped around a cardboard tube as shown below. Checkpoint 2 b In which direction does the magnetic field point inside the tube? A. Left B. Right C. Up D. Down E. Out of screen Use the right hand rule and curl your fingers along the direction of the current. : 22 Physics 212 Lecture 15, Slide 16


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Simulation : 23 Physics 212 Lecture 15, Slide 17




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Solenoid Several loops packed tightly together form a uniform magnetic field inside, and nearly zero magnetic field outside. 1 2 4 3 From this simulation, we can assume a constant field inside the solenoid and zero field outside the solenoid, and apply Ampere’s law to find the magnitude of the constant field inside the solenoid !! : 28 n = # turns/length Physics 212 Lecture 15, Slide 18


Example Problem y I What is the current density j (Amp/m 2) in the conductor? (A) (B) a b x (C) j = I / area : 40 Physics 212 Lecture 15, Slide 24