w07d1 presentation s13 v01 jwb
DESCRIPTION
Presentation of interesting thingsTRANSCRIPT
-
*W07D1Magnetic Dipoles, Force and Torque on a Dipole, Experiment 2W07D1 Magnetic Dipoles, Torque and Force on a Dipole, Experiment 2: Magnetic Dipole in a Helmholtz Coil http://web.mit.edu/8.02t/www/materials/Experiments/expMagForcesDipoleHelmholtz.pdf
Reading Course Notes: Sections 8.4, 8.6.4, 8.10.4, 8.13, 9.5, 9.9
-
Announcements
Exam Two Reviews:Monday from 7-9 pm in 26-152Tuesday from 9-11 pm in 26-152Wednesday from 9-11 pm in 26-152
PS 6 due W07 Tuesday at 9 pm in boxes outside 32-082 or 26-152
Exam 2 Thursday March 21 7:30 - 9:30 pm: See announcement pages for section room assignments
Conflict Friday March 22 9-11 am in 32-082; 10-12 noon in 6-120
*
-
*Magnetic Field of Bar Magnet(1) A magnet has two poles, North (N) and South (S)(2) Magnetic field lines leave from N, end at S
-
*Magnetism Bar MagnetLike poles repel, opposite poles attract
-
*Bar Magnets Are Dipoles!NO! Magnetic monopoles do not exist in isolation Create Dipole Field Rotate to orient with FieldIs there magnetic mass or magnetic charge?
-
*Magnetic Monopoles?Magnetic monopoles do not exist in isolationq-qElectric DipoleWhen cut: 2 monopoles (charges)Magnetic DipoleWhen cut: 2 dipolesAnother Maxwells Equation! (2 of 4)Gausss LawMagnetic Gausss Law
-
*Conservation of Magnetic Flux:
-
*Torque on a Current Loop in a Uniform Magnetic Field
-
If the wire is a uniform magnetic field then
If the wire is also straight then*Review: Magnetic Force on Current-Carrying Wire
-
*Group Problem: Current LoopPlace rectangular current loop in uniform B field 1)What is the net force on this loop?2)What is the net torque on this loop?3)Describe the motion the loop makes
-
*Torque on Rectangular LoopNo net force but there is a torqueArea vector
-
Magnetic Dipole Momenthttp://web.mit.edu/viz/EM/visualizations/magnetostatics/calculatingMagneticFields/RingMagField/RingMagField.htm
-
*Torque on Current LoopPlace rectangular current loop in uniform B field Magnetic moment points out of the page
torque tries to align the magnetic moment vector in the direction of the magnetic field
-
*Concept Question: Magnetic Field LinesThe picture shows the field lines outside a permanent magnet The field lines inside the magnet point:UpDownLeft to rightRight to leftThe field inside is zeroI dont know
-
*Concept Q. Answer: Magnetic Field LinesMagnetic field lines are continuous.E field lines begin and end on charges.There are no magnetic charges (monopoles) so B field lines never begin or endAnswer: 1. They point up inside the magnet
-
*Demonstration:Deflection of a Compass Needle by a Magnet G1http://tsgphysics.mit.edu/front/?page=demo.php&letnum=G%201&show=0
-
*Demonstration:Galvanometer principle G10 http://tsgphysics.mit.edu/front/?page=demo.php&letnum=G%2010&show=0
-
*Concept Question: Dipole in FieldmFrom rest, the coil above will:
rotate clockwise, not moverotate counterclockwise, not movemove to the right, not rotatemove to the left, not rotatemove in another direction, without rotatingboth move and rotateneither rotate nor moveI dont know
-
*Concept Q. Answer: Dipole in FieldAnswer: 1. Coil will rotate clockwise (not move) No net force so no center of mass motion. BUT Magnetic dipoles rotate to align with external field (think compass)
-
*Force on a Dipole in a Non-Uniform Field
-
*Dipoles dont move???This dipole rotates but doesnt feel a net forcein a uniform magnetic fieldBut dipoles can feel magnetic force.
-
*Dipoles in Non-Uniform Fields:Magnetic Force
-
*Concept Question: Dipole in FieldThe current carrying coil above will feel a net forceupwardsdownwardsof zeroI dont know
-
*Concept Q. Answer: Dipole in FieldAnswer: 2. Feels downward force. The forces shown produce a net downward force
-
*Force on Magnetic DipoleWhat makes the field pictured? Bar magnet below dipole, with N pole on top. It is aligned with the dipole pictured, they attract! NSm
-
Work Done by Interaction to Anti-align Magnetic Dipole*
-
Potential Energy: Dipole in Magnetic Field*Set zero reference point Lowest energy state (aligned) : Highest energy state (anti-aligned):
-
*Force on Magnetic DipoleNSNSalong z-axism
-
Magnetic Field Profiles Experiment 2
-
Concept Question: Dipole in HelmholtzA dipole pointing along the positive x-direction and located at the center of a Helmholtz coil will feel:a force but not a torque.a torque but not a force.both a torque and a force.neither force nor torque.
-
Concept Q. Answer: Dipole in HelmholtzAnswer: 2. a torque but not a force. The Helmholtz coil makes a UNIFORM FIELD.Dipole feels only torque (need gradient for force).
-
Concept Question: Dipole in Anti-Helmholtz CoilA dipole pointing along the positive z-direction and located at the center of an anti- Helmholtz coil will feel:a force but not a torque.a torque but not a force.both a torque and a force.neither force nor torque.
-
Concept Q. Answer: Dipole in Anti-Helmholtz CoilAnswer: 1. A force because there is a gradient in the magnetic field but no torque because the magnetic field at the center is zero.
-
Experiment 2:Magnetic Forces on Dipolein Fields of Helmholtz Coil
-
Getting Started: Set up current supplyOpen circuit (disconnect a lead)
Turn current knob full CCW (off)
Increase voltage to ~12 VThis will act as a protection: V
-
Appendix Experiment 2:Magnetic Forces on Dipolein Fields of Helmholtz Coil
Field Configurations and Concept Questions
-
Appendix 2:Gausss Law for Magnetism
-
*Animation: Magnetic Field Generated by a Current Loophttp://web.mit.edu/viz/EM/visualizations/magnetostatics/calculatingMagneticFields/RingMagInt/RingMagIntegration.htm
-
*Demonstration:Magnetic Field Linesfrom Bar Magnet G2http://tsgphysics.mit.edu/front/?page=demo.php&letnum=G%202&show=0
Class 18*Class 18Class 15*Class 18Class 12*Class 18Class 12*Class 18Class 12*Class 18Class 12*Class 18Class 12*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 15*Class 18Class 18*Class 18Class 15*Class 18Class 15*Class 18Class 12*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18Class 18*Class 18\begin{vmatrix}\vec{\tau}\end{vmatrix} = \mu B \sin \thetaW = -\int_0^\pi \tau d\theta = -\int_0^\pi \mu B \sin \theta \,d\theta
Class 15*Class 18Class 18*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Week 08, Day 2Week 08, Day 2Class 19Class 19*Week 08, Day 2Class 19*Class 18Class 18*Class 18Class 12*Class 18