# Phys 133 -- Chapter 321 Chapter 33 Magnetic Field.

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Phys 133 -- Chapter 321 Chapter 33 Magnetic Field

Phys 133 -- 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

Phys 133 -- Chapter 323 Demo magnets

Phys 133 -- Chapter 324 Orients a compass Magnetism: experiments 1

Phys 133 -- Chapter 325 Magnetism: experiments 2

Phys 133 -- Chapter 326 Do Workbook 32.1, 3 & 4

Phys 133 -- Chapter 327 Magnetic field: wire Current produces a magnetic field too - same as magnet Right thumb rule

Phys 133 -- Chapter 328 Thumb along, fingers around (think circles!) Magnetic field: symbol conventions In general

Phys 133 -- Chapter 329 Magnetic field: vectors and field lines Arrow indicates direction compass north would point. Longer arrow, larger field Closer spacing, larger field

Phys 133 -- Chapter 3210 Do Workbook 32.7 & 8

Phys 133 -- Chapter 3211 Moving charges produce magnetic fields Magnet field: cause (cross product, 3D) remember

Phys 133 -- Chapter 3212 Do Workbook 32.11 & 12

Phys 133 -- Chapter 3213 What are the magnetic field strength and direction at the dot in the figure? Problem 32.7

Phys 133 -- Chapter 3214 Problem 32.7 (ans) Direction-RHR = out of page

Phys 133 -- Chapter 3215 --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

Phys 133 -- Chapter 3216 Find an expression for the magnetic field at the center (P) of the circular arc. Problem 32.50

Phys 133 -- Chapter 3217 Problem 32.50 (ans) 1 2 3 For entire loop Direction into page (RHR)

Phys 133 -- Chapter 3218 d Magnetic fields: typical situations

Phys 133 -- Chapter 3219 Demo loop

Phys 133 -- Chapter 3220 Magnetic dipole A current loop

Phys 133 -- Chapter 3221 Do Workbook 32.18,19, 20

Phys 133 -- Chapter 3222 --always true --sometimes helpful (high symmetry) Ampere’s law (Currents cause magnetic fields)

Phys 133 -- Chapter 3223 Take a segment of path, dot product with field, write it down, find another segment, repeat, add up Path integrals

Phys 133 -- Chapter 3224 Do Workbook 32.23 & 24

Phys 133 -- Chapter 3225 --always true --sometimes helpful (high symmetry) Ampere’s law (Currents cause magnetic fields)

Phys 133 -- 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

Phys 133 -- 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

Phys 133 -- Chapter 3228 Solenoid

Phys 133 -- Chapter 3229 Uniform inside, “zero” out Solenoid

Phys 133 -- Chapter 3230 Force on moving charge

Phys 133 -- Chapter 3231 Do Workbook 32.27 & 28

Phys 133 -- Chapter 3232 Demo Tesla Coil

Phys 133 -- 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

Phys 133 -- Chapter 3234 Problem 32.31 (ans) Direction RHR

Phys 133 -- Chapter 3235 Do Workbook 32.29 & 31

Phys 133 -- 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

Phys 133 -- 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

Phys 133 -- Chapter 3238 Force on current-carrying wire

Phys 133 -- Chapter 3239 Demo wire in magnetic field

Phys 133 -- Chapter 3240 Do Workbook 32.35 & 37

Phys 133 -- Chapter 3241 Force/torque on current loop

Phys 133 -- Chapter 3242 Do Workbook 32.40 & 41

Phys 133 -- Chapter 3243 Magnetic material and induced dipole