Chapter 11 section 2 Electric power distribution PDF

Preview

Summary

Chapter 11 part 2 lecture notes ...

Description

Chapter(11(section(2(((Electric(Power(Distribution( ( 1.(Connections(between(electricity(and(magnetism.( ( 2.(The(Oersted(experiment(1820.(Demonstration.( ( A(current(in(a(wire(will(produce(a(magnetic(field.(It(can(deflect( a(compass(needle.( ( 3.(Magnetic(induction--((a(changing(magnetic(can(produce(an( electric(field.(Demonstration.( ( 4.(Self-induction(in(a(coil.( The(induced(electric(field(always(produces(a(magnetic(field( that(opposes(the(current(trying(to(create(the(magnetic(field(in( the(coil.( ( 5.(This(opposition(to(change(is(called(Lenz’s(Law.( It(has(parallels(in(chemistry,(economics,(sociology(and( anthropology.( ( 6.(All(coils(have(a(self-inductance(that(limits(the(build(up(of(a( current(in(the(inductor,(just(as(the(capacitance(slows(down(the( build(up(of(charge(on(a(capacitor.( ( 7.(To(create(a(current(in(an(inductor((coil)(requires(energy.( This(energy(is(stored(in(the(magnetic(field(in(the(inductor.( ( Energy(=(magnetic(field2(x(volume/2x(permeability(of(free( space( ( U(=(B2(x(V/2(x(µ0( (

In(fact,(wherever(there(are(magnetic(fields(energy(is(stored,( even(in(empty(space.(Space(is(full(of(magnetic(fields.(In(the( future(the(energy(stored(in(these(magnetic(fields(may(be(used( to(power(spaceships!( ( (

8.(Transformers( ( Think(of(2(coils,(sometimes(referred(to(as(solenoids,(arranged( parallel(to(each(other.( A(current(flowing(through(the(left(solenoid(will(produce(a( magnetic(field(in(that(solenoid(as(well(as(a(magnetic(field(in(the( right(solenoid.( If(the(current(in(the(left(solenoid((the(primary)(is(an(AC( current,(the(magnetic(fields(in(both(solenoids(will(be(changing.( This(changing(magnetic(field(in(the(right(solenoid((the( primary)(will(induce(a(voltage(in(the(secondary.(Depending(on( the(ratio(of(the(number(of(turns(in(the(primary(to(the(number( of(turns(in(the(secondary,(the(induced(voltage(in(the(secondary( can(be(greater((step(up(transformer),(or(less(than(in(the( primary((step(down(transformer).( ( 9.(Electric(Power(Distribution( ( The(power(produced(at(an(electric(utility(is(measured(in( gigawatts.(One(gigawatt(equals(a(billion(watts.(Power(=(VI.( Typically,(V(is(5,000(V,(and(the(current(is(in(the(thousands(of( amperes.( When(the(power(is(shipped(from(the(plant(to(users,(the( transmission(lines(heat(up.(The(loss(is(equal(to(I2R.(Therefore( utilities(want(the(power(lines(to(be(at(low(current(and(high( voltage,(typically(500,000(volts.(So(a(step(up(transformer(is( needed.(Once(the(transmission(lines(reach(their(intended( destinations,(the(voltage(has(to(be(reduced(to(120(V((in(Europe( to(230(V),(which(requires(a(step(down(transformer.(

(...