Chapter 33 Magnetic Field Phys 133 -- Chapter 32
The questions What are magnetic phenomena? What causes magnetic fields? Magnetic field of moving charges/currents Magnetic force on moving charges/currents Magnetic torque Magnetic materials Phys 133 -- Chapter 32
Demo magnets Phys 133 -- Chapter 32
Magnetism: experiments 1 Orients a compass Phys 133 -- Chapter 32
Magnetism: experiments 2 Phys 133 -- Chapter 32
Do Workbook 32.1, 3 & 4 Phys 133 -- Chapter 32
Magnetic field: wire Current produces a magnetic field too - same as magnet Right thumb rule Phys 133 -- Chapter 32
Magnetic field: symbol conventions In general Thumb along, fingers around (think circles!) Phys 133 -- Chapter 32
Magnetic field: vectors and field lines Arrow indicates direction compass north would point. Longer arrow, larger field Closer spacing, larger field Phys 133 -- Chapter 32
Do Workbook 32.7 & 8 Phys 133 -- Chapter 32
Magnet field: cause remember (cross product, 3D) Moving charges produce magnetic fields Phys 133 -- Chapter 32
Do Workbook 32.11 & 12 Phys 133 -- Chapter 32
Problem 32.7 What are the magnetic field strength and direction at the dot in the figure? Phys 133 -- Chapter 32
Problem 32.7 (ans) Direction-RHR = out of page Phys 133 -- Chapter 32
Magnetic field: current segment Current (many moving charges) produce magnetic fields To find magnetic field produced by a wire configuration --pick a generic current segment --field due to segment at location of interest --convert current segment to coordinate --sum them up, becomes integral Phys 133 -- Chapter 32
Problem 32.50 Find an expression for the magnetic field at the center (P) of the circular arc. Phys 133 -- Chapter 32
Problem 32.50 (ans) 3 2 1 Direction into page (RHR) For entire loop Phys 133 -- Chapter 32
Magnetic fields: typical situations d Phys 133 -- Chapter 32
Demo loop Phys 133 -- Chapter 32
Magnetic dipole A current loop Phys 133 -- Chapter 32
Do Workbook 32.18,19, 20 Phys 133 -- Chapter 32
Ampere’s law (Currents cause magnetic fields) --always true --sometimes helpful (high symmetry) Phys 133 -- Chapter 32
Path integrals Take a segment of path, dot product with field, write it down, find another segment, repeat, add up Phys 133 -- Chapter 32
Do Workbook 32.23 & 24 Phys 133 -- Chapter 32
Ampere’s law (Currents cause magnetic fields) --always true --sometimes helpful (high symmetry) Phys 133 -- Chapter 32
Problem Ampere A long wire is surrounded by a thin cylindrical shell of radius R1. The inner wire carries a current I0 in one direction and the outer shell carries a current I0 in the other direction. Use Ampere’s law to find the magnetic field strength everywhere. Phys 133 -- Chapter 32
Problem Ampere (ans) Side view I0 (out) • R1 • • x Then I0 (in) • B is circular (RTR) Choose concentric circle as path r < R1 Ampere’s law becomes R1 < r Phys 133 -- Chapter 32
Solenoid Phys 133 -- Chapter 32
Solenoid Uniform inside, “zero” out Phys 133 -- Chapter 32
Force on moving charge Phys 133 -- Chapter 32
Do Workbook 32.27 & 28 Phys 133 -- Chapter 32
Demo Tesla Coil Phys 133 -- Chapter 32
Problem 32.31 An electron moves in the magnetic field B=0.50 i T with a speed of 1.0x107m/s in the direction shown. What is the magnetic force (in component form) on the electron? Phys 133 -- Chapter 32
Problem 32.31 (ans) Direction RHR Direction RHR Phys 133 -- Chapter 32
Do Workbook 32.29 & 31 Phys 133 -- Chapter 32
Problem Velocity Selector 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 v0 will pass through undeflected and without speeding up. (easy one: E=0, B=0) Phys 133 -- Chapter 32
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 ay = 0 Phys 133 -- Chapter 32
Force on current-carrying wire Phys 133 -- Chapter 32
Demo wire in magnetic field Phys 133 -- Chapter 32
Do Workbook 32.35 & 37 Phys 133 -- Chapter 32
Force/torque on current loop Phys 133 -- Chapter 32
Do Workbook 32.40 & 41 Phys 133 -- Chapter 32
Magnetic material and induced dipole Phys 133 -- Chapter 32
