Chapter 11 Magnetism - Lecture notes 11 PDF

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Chapter 11 notes on magnetism ...

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Chapter(11(Section(1(Magnetism( (

1. There(are(no(magnetic(monopoles(or(isolated(north(and(south( poles(like(there(are(positive(and(negative(charges.( ( ( 2. If(there(were,(there(would(be(an(equivalent(formula(like( Coulomb’s(Law( P1((((((((((((((((((((p2( ((((((((((((((((((((((((((((((((((((r( ( ( F=µ0(p1(p2/4πr2(( ( µ0(is(called(the(permeability(of(free(space(and(has(the(value(4π(x(10-7(( N/A2( ( ( 3. Instead(there(are(magnetic(dipoles.(A(bar(magnet(is(a(dipole(with( a(north(and(a(south(pole.( ( The(earth(acts(like(it(had(a(bar(magnet(in(it(creating(a(dipole(magnetic( field.(The(unit(of(magnetic(field(is(the(Tesla.(The(magnetic(field(of(the( earth(is(about(5x10-4(Tesla.( ( This(was(first(verified(by(William(Gilbert,(the(personal(physician(to( Elizabeth(I.( ( ( 4.(Demonstrations(of(magnetic(field(of(a(bar(magnet.(( A(piece(of(wire(bent(in(a(circle(and(carrying(a(current(also(creates(a( dipole(field.((See(Bloomfield(page(312.( ( This%implies%that%there%are%currents%in%the%center%of%the%earth.( ( ( 5.An(elementary(particle(like(an(electron,(proton(and(neutron,(spin( about(a(vertical(axis.(Their(charge(therefore(produces(a(current.(The(

protons(in(your(body(act(like(little(magnets.(They(can(absorb(energy( and(flip.(That’s(what(happens(in(an(MRI(magnet.(You(can(image(the( water(molecules(in(your(body.(The(magnetic(field(in(an(MRI(magnet( is(1-2(Tesla.( NYU(has(a(7(Tesla(magnet(on(38th(St.( It(can(flip(the(spins(in(other(atoms(other(than(hydrogen(and(see(them( in(the(body.( ( 6.(If(you(place(one(end(of(a(long(bar(magnet(in(a(strong(magnetic(field( it(will(experience(a(force(like(a(charged(particle(in(an(electric(field.( ( Magnetostatic(force(=(pole(x((magnetic(field(((F=(p(B( ( See(“Careful(with(that(wrench”(on(page(310.(With(p=1000(Am,(and( B=(1(Tesla,(F(is(1000(N(about(225(lb.( ( 7.(Atoms(in(your(body(contain(electrons(and(therefore(behave(like(( little(magnets.(In(some(materials(called(ferromagnetic(the(atoms(line( up(in(a(domain(producing(a(strong(magnetic(field.(In(most(other( materials(the(electros(pair(off(with(opposite(spins,(( cancelling(the(atom’s(magnetic(behavior.( ( 8.(The(atoms(in(the(periodic(table(with(atomic(numbers(57-72(are( called(rare(earth(elements.(They(can(have(as(many(as(7(unpaired( electrons.(Button(magnets(of(these(materials(can(produce(magnetic( fields(of(6(Tesla.(One(button(magnet(placed(upside(down(above( another(button(magnet(can(levitate.( ( ( ( ( ( (...