Download Resonance in AC Circuits and Electromagnetic Waves and more Study notes Physics in PDF only on Docsity! Physics 102: Lecture 14, Slide 1 Resonance Electromagnetic Waves • Today’s lecture will cover Textbook Sections 21.6, 22.1, 4-5, 9 Physics 102: Lecture 14 Physics 102: Lecture 14, Slide 2 Review: Impedance Triangle and Resonance R (XL-XC) Z φ XL and XC point opposite. When adding, they tend to cancel! When XL = XC they completely cancel and Z = R. This is resonance! Imax(XL-XC) ImaxXL ImaxXC ImaxR V gen,m ax φ Vmax,gen = Imax Z Physics 102: Lecture 14, Slide 5 Preflight 14.1 As the frequency of the circuit is either raised above or lowered below the resonant frequency, the impedance of the circuit: L R CAlways increases Resonance in AC Circuits frequency Only increases for lowering the frequency Only increases for raising the frequency f0 Z Physics 102: Lecture 14, Slide 6 ACT: Resonance The AC circuit to the right is being driven at its resonance frequency. Compare the maximum voltage across the capacitor with the maximum voltage across the inductor. 1) VC > VL 2) VC = VL 3) VC < VL 4) Depends on R L R C Physics 102: Lecture 14, Slide 7 Preflight 14.3 At the resonant frequency, which of the following is true? I is in phase with Vgenerator I leads Vgenerator I lags Vgenerator VL VC VR Vgen φ = 0 Physics 102: Lecture 14, Slide 10 Electromagnetic Waves + - Direction wave travels Generator creates E field up and down. Physics 102: Lecture 14, Slide 11 ACT: EM Waves Which direction should I orient my antenna to receive a signal from a vertical transmission tower? 1) Vertical 2) Horizontal 3) 45 Degrees + - Direction wave travels Physics 102: Lecture 14, Slide 12 Electromagnetic Waves (Preflight 14.5) Generator also creates B field into and out of the page! x z y + - Physics 102: Lecture 14, Slide 15 EM Waves Practice E x Shown below is the E field of an EM wave broadcast at 96.1 MHz and traveling to the right. (1) What is the direction of the magnetic field? (2) Label the two tic marks on the x axis (in meters). Physics 102: Lecture 14, Slide 16 Doppler Effect • fo = fe (1 + u/c) moving toward each other • fo = fe (1 - u/c) moving away from each other Note: These are easier than equations for sound! • Finding relative velocity: u = v1 + v2 moving in opposite directions u = v1 – v2 moving in same direction observed frequency emitted frequency Physics 102: Lecture 14, Slide 17 Doppler Practice V = 32 m/s V = 50 m/s In the jeep, the frequency of the light from the troopers car will appear: (1) higher (more blue) (2) Lower (more red) What value should you use for u in the equation? (1) 32 (2) 50 (3) 50+32 (4) 50-32
