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Phys 133 -- Chapter 321 Chapter 33 Magnetic Field.

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Presentation on theme: "Phys 133 -- Chapter 321 Chapter 33 Magnetic Field."— Presentation transcript:

1 Phys Chapter 321 Chapter 33 Magnetic Field

2 Phys Chapter 322 What are magnetic phenomena? What causes magnetic fields? Magnetic field of moving charges/currents Magnetic force on moving charges/currents Magnetic torque Magnetic materials The questions

3 Phys Chapter 323 Demo magnets

4 Phys Chapter 324 Orients a compass Magnetism: experiments 1

5 Phys Chapter 325 Magnetism: experiments 2

6 Phys Chapter 326 Do Workbook 32.1, 3 & 4

7 Phys Chapter 327 Magnetic field: wire Current produces a magnetic field too - same as magnet Right thumb rule

8 Phys Chapter 328 Thumb along, fingers around (think circles!) Magnetic field: symbol conventions In general

9 Phys Chapter 329 Magnetic field: vectors and field lines Arrow indicates direction compass north would point. Longer arrow, larger field Closer spacing, larger field

10 Phys Chapter 3210 Do Workbook 32.7 & 8

11 Phys Chapter 3211 Moving charges produce magnetic fields Magnet field: cause (cross product, 3D) remember

12 Phys Chapter 3212 Do Workbook & 12

13 Phys Chapter 3213 What are the magnetic field strength and direction at the dot in the figure? Problem 32.7

14 Phys Chapter 3214 Problem 32.7 (ans) Direction-RHR = out of page

15 Phys Chapter pick a generic current segment --field due to segment at location of interest --convert current segment to coordinate --sum them up, becomes integral Magnetic field: current segment Current (many moving charges) produce magnetic fields To find magnetic field produced by a wire configuration

16 Phys Chapter 3216 Find an expression for the magnetic field at the center (P) of the circular arc. Problem 32.50

17 Phys Chapter 3217 Problem (ans) For entire loop Direction into page (RHR)

18 Phys Chapter 3218 d Magnetic fields: typical situations

19 Phys Chapter 3219 Demo loop

20 Phys Chapter 3220 Magnetic dipole A current loop

21 Phys Chapter 3221 Do Workbook 32.18,19, 20

22 Phys Chapter always true --sometimes helpful (high symmetry) Ampere’s law (Currents cause magnetic fields)

23 Phys Chapter 3223 Take a segment of path, dot product with field, write it down, find another segment, repeat, add up Path integrals

24 Phys Chapter 3224 Do Workbook & 24

25 Phys Chapter always true --sometimes helpful (high symmetry) Ampere’s law (Currents cause magnetic fields)

26 Phys Chapter 3226 A long wire is surrounded by a thin cylindrical shell of radius R 1. The inner wire carries a current I 0 in one direction and the outer shell carries a current I 0 in the other direction. Use Ampere’s law to find the magnetic field strength everywhere. Problem Ampere

27 Phys Chapter 3227 Problem Ampere (ans) x I 0 (in) I 0 (out) R1R1 Side view Choose concentric circle as path B is circular (RTR) Then Ampere’s law becomes r < R 1 R 1 < r

28 Phys Chapter 3228 Solenoid

29 Phys Chapter 3229 Uniform inside, “zero” out Solenoid

30 Phys Chapter 3230 Force on moving charge

31 Phys Chapter 3231 Do Workbook & 28

32 Phys Chapter 3232 Demo Tesla Coil

33 Phys Chapter 3233 An electron moves in the magnetic field B=0.50 i T with a speed of 1.0x10 7 m/s in the direction shown. What is the magnetic force (in component form) on the electron? Problem 32.31

34 Phys Chapter 3234 Problem (ans) Direction RHR

35 Phys Chapter 3235 Do Workbook & 31

36 Phys Chapter 3236 Find the strength and direction of electric and magnetic fields confined to the dashed region, such that a charged particle (q>0, m) coming from the left at speed v 0 will pass through undeflected and without speeding up. (easy one: E=0, B=0) Problem Velocity Selector

37 Phys Chapter 3237 Problem Velocity Selector (ans) E + Put electric field down Then Need force up if proton is to be undeflected Put magnetic field into page Then We want a y = 0

38 Phys Chapter 3238 Force on current-carrying wire

39 Phys Chapter 3239 Demo wire in magnetic field

40 Phys Chapter 3240 Do Workbook & 37

41 Phys Chapter 3241 Force/torque on current loop

42 Phys Chapter 3242 Do Workbook & 41

43 Phys Chapter 3243 Magnetic material and induced dipole


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