# Fig 33-CO, p.1033. Ch 33 Alternating Current Circuits 33.1 AC Sources and Phasors v = V max sint  = 2/T = 2f tt V max v = V max sint Phasor.

## Presentation on theme: "Fig 33-CO, p.1033. Ch 33 Alternating Current Circuits 33.1 AC Sources and Phasors v = V max sint  = 2/T = 2f tt V max v = V max sint Phasor."— Presentation transcript:

Fig 33-CO, p.1033

Ch 33 Alternating Current Circuits 33.1 AC Sources and Phasors v = V max sint  = 2/T = 2f tt V max v = V max sint Phasor

CT1: The phasor diagrams below represent three oscillating voltages having different amplitudes and frequencies at a certain instant of time t = 0. As t increases, each phasor rotates counterclockwise and completely determines a sinusoidal oscillation. At the instant of time shown, the instantaneous value of v associated with each phasor is given in ascending order by diagrams A. a,b,c. B. a,c,b. C. b,c,a. D. b,a,c. E. c,a,b F. c,b,a

CT2: Consider the pairs of phasors below, each shown at t = 0. All are characterized by a common frequency of oscillation . If we add the oscillations, the maximum amplitude is achieved for pair(s) A. a. B. b. C. c. D. d. E. e. F. c and d. G. a and c. H. b and c.

Ch 33 Alternating Current Circuits 33.2 Resistors in an AC Circuit i R = v R /R = V max sint/R = I max sint I max = V max /R

Ch 33 Alternating Current Circuits 33.2 Resistors in an AC Circuit I rms = I max /2 1/2 V rms = V max /2 1/2 P av = P rms = I rms 2 R = V rms 2 /R V rms = I rms R P33.2 (p.946) P33.4 (p.946)

Ch 33 Alternating Current Circuits 33.3 Inductors in an AC Circuit v L = V max sint I max = V max /L i L = I max sin(t - /2) lags voltage by /2 P33.11 (p.946) X L = L I max = V max /X L

Ch 33 Alternating Current Circuits 33.4 Capacitors in an AC Circuit v L = V max sint I max = CV max i C = I max sin(t + /2) leads voltage by /2 P33.15 (p.946) X C = 1/C I max = V max /X C

CT3: The light bulb has a resistance R, and the emf drives the circuit with a frequency . The light bulb glows most brightly at A. very low frequencies. B. very high frequencies. C. the frequency  = (1/LC) 1/2

Fig 33-14, p.1044

Ch 33 Alternating Current Circuits 33.5 RLC Series Circuit v = V max sint I max = V max /Z i = I max sin(t - ) I lags voltage by  Z = (R 2 + (X L – X C ) 2 ) 1/2  = tan -1 [(X L –X C )/R] i

P33.17 (p.946) P33.27 (p.947)

Ch 33 Alternating Current Circuits 33.6 Power in an AC Circuit P av = P rms = I rms V rms cos cos is called the power factor Check P33.27 (p.947) i

Ch 33 Alternating Current Circuits 33.7 Resonance in a Series RLC Circuit P av = V rms 2 R/(R 2 + L 2 ( 2 -  0 2 ) 2 / 2 )  0 = (1/LC) 1/2 Q =  0 /  = R/L i

CT4: For the RLC series circuit shown, which of these statements is/are true: (i) Potential energy oscillates between C and L. (ii) The source does no net work: Energy lost in R is compensated by energy stored in C and L. (iii) The current through C is 90° out of phase with the current through L. (iv) The current through C is 180° out of phase with the current through L. (v) All energy is dissipated in R. A. all of them B. none of them C. (v) D. (ii) E. (i), (iv), and (v) F. (i) and (v) G. none of the above

P33.38 (p.948)

Ch 33 Alternating Current Circuits 33.8 The Transformer and Power Transmission V 2 = N 2 V 1 /N 1 Ideal Transformer: P pri = I 1 V 1 = P sec = I 2 V 2 P33.41 (p.948) i V2V2

CT5: When the switch is closed, the potential difference across R is A. V(N2 /N1). B. V(N1/N2). C. V. D. zero. E. insufficient information

CT6: The primary coil of a transformer is connected to a battery, a resistor, and a switch. The secondary coil is connected to an ammeter. When the switch is thrown closed, the ammeter shows A. zero current. B. a nonzero current for a short instant. C. a steady current.

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