PHY 2049 Physics II n n Tutoring Center

  • Slides: 16
Download presentation
PHY 2049: Physics II n n Tutoring Center is open in room NPB 1100,

PHY 2049: Physics II n n Tutoring Center is open in room NPB 1100, M-F 10: 00 AM -3: 00 PM. It is free. Hopefully all webassign problems have been solved. Please see me immediately after the class if there is still an issue.

PHY 2049: Physics II n About bicycle riding: If some one shows you a

PHY 2049: Physics II n About bicycle riding: If some one shows you a trick, it means that, n n It is possible to do that trick The person who showed you, can do the trick. It does not mean that you can do the trick. Try it a lot of times and you can too.

PHY 2049: Physics II Recall: n n Faraday’s law Lenz’ law: the kickback

PHY 2049: Physics II Recall: n n Faraday’s law Lenz’ law: the kickback

PHY 2049: Physics II n n Recall more Inductors and inductance n n n

PHY 2049: Physics II n n Recall more Inductors and inductance n n n RL circuits n n Emf induced in a coil when the current changes Solenoids L = μ 0 n 2 l. A I = (1 -e-t/τ)V/Rτ = L/R Energy in a magnetic field U = ½ Li 2, u = B 2/2μo In a coaxial cable the surface is most stressed.

PHY 2049: Physics II n Mutual induction E 2 = -M 21 di 1

PHY 2049: Physics II n Mutual induction E 2 = -M 21 di 1 /dt M 21 = M 12 n Coil in a coil n n

PHY 2049: Physics II n Three circuit elements: n n Capacitor Resistor Inductor V

PHY 2049: Physics II n Three circuit elements: n n Capacitor Resistor Inductor V = Q/C V = IR I = d. Q/dt V =- Ld. I/dt A general circuit is a combination of these elements. The analysis is a bit subtle.

PHY 2049: Physics II

PHY 2049: Physics II

PHY 2049: Physics II a. Long after the switch is closed b. In each

PHY 2049: Physics II a. Long after the switch is closed b. In each case the current through R is shorted by the inductor. The inductor carries all of the current. c. b. Switch is opened. The equivalent resistances are (1) R (2) 2 R and (3) R/2. Hence by current, the ranking is 3 1 2. d. c. Long after the switch is opened, there is no current anywhere.

PHY 2049: Physics II

PHY 2049: Physics II

PHY 2049: Physics II Problem 32: The area is v 2 t 2, you

PHY 2049: Physics II Problem 32: The area is v 2 t 2, you can convince yourself that the two sides of the triangle are each 2 vt/√ 2. Area A = ½ (2 vt/√ 2)2 At t= 3 s. Flux = BA = 0. 35 x 5. 22 x 32 = 85. 2 Wb Emf around: 56. 8 V Emf = 18. 93 t. , n = 1

PHY 2049: Physics II n n L 1 L 2 L 3 L 4

PHY 2049: Physics II n n L 1 L 2 L 3 L 4 = = 30 50 20 15 m. H

PHY 2049: Physics II n n L 1 L 2 L 3 L 4

PHY 2049: Physics II n n L 1 L 2 L 3 L 4 = = 30 50 20 15 m. H L 23 = 14. 3 Leq = 30 +15 + 14. 3 = 59. 3 m. H

PHY 2049: Physics II

PHY 2049: Physics II

PHY 2049: Physics II n n n E =Ldi/dt i = Et/L t =

PHY 2049: Physics II n n n E =Ldi/dt i = Et/L t = i. L/E = 1. 5 s

PHY 2049: Physics II n LC oscillations n n For a spring n n

PHY 2049: Physics II n LC oscillations n n For a spring n n n Ld 2 Q/dt 2 +Q/C = = Md 2 x/dt 2 +kx =0 Solution is x = A cosωt ω = √(k/m) Here ω = 1/ √(LC) When there is a natural frequency, there is violent response => resonance Quantity mech Mass m Spring k Position x electronic L 1/C Q

PHY 2049: Physics II n n Inductors and inductance Currents are slowed down by

PHY 2049: Physics II n n Inductors and inductance Currents are slowed down by Faraday’s law Eddy currents More later