Chapter 19 MagnetismHard-magnetic material difficult to magnetize. Retain magnetism (permanent)Soft- magnetic material, easy to magnetize, lose magnetism easilyMotion if a charged particle in a magnetic field. the magnetic force is always directed toward the center ofthe circular path; therefore, the magnetic force causes a centripetal acceleration,which changes only the direction of vSand not its magnitudeMagnetic field – Defined by force felt by test chargemoving with velocity v.FB=qvBsinθ(T) 1 Gauss= 10-4Magnetics field due to a long, straight wireused only when current & magneticfield are at right angles to one other Magnitude of Magnetic ForceAmperes Circuit Law Two long parallel wires apart carry the same current and the magnetic force per unit of length each wire 2*10^-7 Amperes-when 2 parallel 1m apart carry the same current and magnetic force per unit length each wire is Torque on Current loopτ =BIANsin θ=μBsinθB at angle perpendicular to the plane of the loop.τMAX=BIAMagnetic force between wiresParallel conductors carrying currents in the same direction attract each other Parallel conductors carrying currents in opposite directions repel eachother.EXAMS Q’sSlinky+battery+switch closed, I runs  will not compress/expand will heat up inseadMagnetic field of a current loop Solenoid (electromagnet) inside n=N/lChapter 20 Induced Voltages & Inductance Moving charges can generate a magnetic field Moving magnet  induce electric current INDUCED EMF-changing magnetic fieldMAGNETIC FLUX - #magnetic field lines(perpendicular)ΦB=BAcosθ Btwn normal n B(Perpendicular only BA) (Wb,weber= Tm2) Faraday’s Law Can cause change in magnetic flux 1.loop A 2.B3. angle btwn A n Bε=N|ΔΦB|Δ tLenz’s Law- current caused by the induced emf making Bthat oppose the original change in flux thro circuitGenerator= motor run “in reverse”; loop roatedby external means Emf insuced into loop makes currentAC generator : Total emf2Bl((a2)ωsinωt=BAωSinωtε=NBAωSinωt;εmax=NBAωε=VmaxSinωtMotional ΔV=emf-|ε|=ΔΦBΔt=BlΔxΔt=BlvI=|ε|R=BlvRSelf-inductance – change in flux is from circuit Self-induced emf-ε=−LΔ IΔt(Vs/A=HENRY H)  L = inductance =l=NΦBiInductance of a SolenoidL=μoN2Al=μon2Al=μon2VRL CircuitsInductor on solenoid measure rate of change of currentTime constantτ =LR=Energy stored in magnetic field Emf from inductor prevents battery from setting instantaneous current in circuit, energy stored in magnetic field PEL=12L I2Chapter 21 Alternating Current Circuits and Electromagnetic WavesResistors in an AC CircuitDC battery power source V=constantAC  ac poer source(generator) V=Vmaxsin(2Пf)Vrms=IrmsR Vmax=ImaxR iR=vR/R *R is constant for all frequencesPower&RMS valueDirection of I no effect on RP=i2R rate of electrical energy dissipated in circuitRms current is direct current dissipates the same amount of energy in the resistor as it was dissipated by the AC current Irms=Imax√2 Pav=I2rms R or Ohm’s Law for R in AC ∆ VRMS=IrmsRSwitch is close intitail charge in capacitor is0Charge accumulateon , V develops opposing I High f less t to charge c, high I ∆ ν=ΔVmaxsin2 πftThe reactance depends on the frequency of the sourceCurrent and voltage don’t go together & Current is same for all components in series: Resonant Frequency: XL=XC so Z=R TrandformersIncreasing current in primary creates an increase in flux thro primary & secondary (Faradays lawFlux same through coils Transformers depend on change in flux only work for alternating currentsHigher V smaller I less power wasted Large currents can be generated with small VrmsInductive reactaceInduced emf:particle a it radiates energy lose energy in EM wavesProperites of EM E & B fields are perpendicular then perpendicular to direction of motion EM WAVES TRANSVERSE WAVES Inductor (L): voltage (E)comes before current (I) • Capacitor (C): current (I) comes before voltage (E) • Phase shiV is 90 degrees for bothThe power dissipated in an AC series ciruit incease as the phase ang;e approaches what value?zzeroEM wave ttravel thro free space speed cannot increase by f, energy, momentumE & B