Physics_Chapter_-_16_(Altern._Current).pptx

Physics 2nd year chapter 16

1. FSC Physics Chapter 16: Alternating Current

2. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

4. Alternating Current Definition: “A.C is the current produced by a voltage source that reverse its polarity with time”. Time Period Of A.C: “Time interval T in which source voltage or current reverse its polarity once”. Graph of A.C: The sinusoidal waveform of A.C is a graph between voltage and time.

6. Types of Current Supplies: Peak Value (V o or I o ): It is the highest value for voltage or current. Peak to Peak Value: It is the sum of +ve and –ve peak value. Supplies AC (Varying Supplies) Saw tooth wave form Sinusoidal wave Square waveform DC (Constant supplies) Steady state DC Pulsating DC

9. Vector Representation of an Alternating Quantity: “Projection of a counter clockwise rotation vector along represents a sinusoidal alternating voltage or current”. Condition of Vector Representation: Scale represent peak or rms value. In a horizontal position alternating quantity is zero or increasing positively. Angular frequency is the same. Vector Diagram: “Length of vector represents the peak value or rms value of signals and angle represents the change in phase in A.C signals”.

10. MCQ: The frequency of A.C in Pakistan is: 30 Hz 50 Hz 60 Hz 120 Hz

11. MCQ: If V represents the peak value of the voltage in an A.C circuit, the rms value of the voltage will be:  

12. MCQ: The rate of heat production in a resistor due to an alternating current of rms value is 10 A is same as that of the direct current of:  

13. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

14. A.C Circuit Electrical Circuit: “A path between two or more points along which an electrical current can be carried”.

15. Types of Electrical Circuit: Features D.C Circuit A.C Circuit 1. Basic element Resistor Resistor Inductor Capacitor 2. Control of circuit Resistor control voltage and current Voltage and current controlled by resistor, inductor and capacitor. 3. Response of circuit Ohm’s law (V = IR) Circuit response when excited by alternating voltage.

16. MCQ: Hot wire ammeter can be used for measuring: Alternating current only Direct current only Both alternating and direct current Neither alternating nor direct current

17. MCQ: When an A.C source is connected across a resistor: The current leads the voltage in phase The current legs behind the voltage in phase The current and voltage in phase None of these

18. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

19. A.C through a Resistor  

20. Characteristic of A.C through a Resistor: Voltage and current are in same phase. If one increases or decreases, the other do the same. Instantaneous Power: In power at any instant in the circuit can be found as; P = I 2 R = VI = V 2 / R These equation satisfied when voltage and current are in same phase.

23. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

24. A.C through a Capacitor Statement: “A circuit in which capacitor is connected in series with switch and A.C source”. Due to D.C, a capacitor behave as insulator and store charge. Due to A.C, a capacitor behave as conductor.

27. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

28. A.C through an Inductor Statement: “A circuit in which inductor is connected in series with switch and A.C source”. Through inductor A.C produces self-inductance effects because it constantly changes.

31. MCQ: In a circuit of inductance of zero resistance, the current leg behind the applied A.C voltage by a phase equal to: 90 o 45 o 30 o o

33. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

34. Impedance  

35. Impedance of different Circuits: Circuit Element Impedance Phase Angle 1. Resistance Z = R o 2. Capacitance +90 o 3. Inductance -90 o 4. R - L 5. R – C 6. RLC

36.   0.4 0.6 0.8 1

37. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

38. R – C and R – L Series Circuits R – C Series Circuits: The circuit in which resistor and capacitor are connected in series with the A.C source. Working: In resistor current I and voltage V are in same phase. In capacitor current I lead the voltage V by phase of 90 o .

42. MCQ: The resistor R and capacitor C are connected in series across as A.C source of rms voltage 5 V. If the rms voltage across C is 3 V than that across R is: 1 V 2 V 3 V 4 V

43. MCQ: An alternating emf is connected across a series combination of a resistance R and an inductance L. If the potential drop across R is 200 V and that across L is 150 V, the applied voltage is:  

44. MCQ: Which of the following graph represents the variations of capacitive reactance X c with the frequency v of the voltage source?

45. MCQ: Which of the following graph represents the variations of inductive reactance X L with the frequency v of the voltage source?

46. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

47. Power in A.C Circuits  

48. MCQ: The power factor of an A.C circuit has the value: Unity when the circuit contains only as inductance Unity when the circuit contains only a resistance Zero when the circuit contains only a resistance Unity when the circuit contains only a capacitance

50. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

51. Series Resonance Circuit  

54. MCQ: In an LRC series circuit, the voltage across R, L and C at resonance are 40 V, 60 V and 60 V respectively. The applied voltage is:  

55. MCQ: In an LCR series circuit, the capacitor is changed from C to 4 C. For the same resonant frequency, the inductance should be changed from L to: 2 L L / 2 L / 4 4 L

56. MCQ: Power delivered by an A.C source of angular frequency as to an LCR series circuit is maintained when:  

57. MCQ: In a LCR A.C circuit off resonance, The current: Is always in phase with the voltage Always lags behind the voltage Always leads the voltage May leads or legs behind the voltage

58. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

59. Parallel Resonance Circuit RLC Parallel Circuit: The circuit in which resistor, capacitor and inductor are connected in parallel way with the A.C source.

61. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

62. Three Phase A.C Supply Statement: In three phase A.C generator, there are three coils inclined at 120 o angle to each other. Each coil is connected to its own pair of slip rings.

63. Properties of three phase A.C supply: In three – phase supply, total load is divided in three parts. There will be no drop of voltage supply in three phases. Three phase supply can provide 400 V between two live wires. The live wire to neutral voltage is 230 V. Star type connection is used to connect three phase wires and one neutral wire.

64. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

65. Principle of Metal Detectors Principle: A coil and a capacitor are electrical component which together can produced oscillation of current. Electrical Oscillator: The circuit in which energy oscillates between a capacitor and an inductor.

66. Working of Metal Detector: Two electrical oscillators Inductance same at resonance frequency (when no object near) Inductance of search coil decrease and frequency increase (when metal close to oscillator B) Beat heard

67. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

68. Choke Statement: It is a coil which consists of thick copper wire wound closely in a large number of turns over a soft iron laminated cores. Properties: It is an inductive coil. It consume extremely small power. It is used in A.C circuit to limit current.

69. MCQ: A chock coil has: High inductance and high resistance High inductance and low resistance Low inductance and high resistance Low inductance and low resistance

70. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

71. Electromagnetic Waves Definition: “The waves which do not required any medium for their propagation”. Introduction to Electromagnetic Waves: Electromagnetic waves were predicted by Maxwell and experimentally produced by Frank Hertz.

73. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

74. Principle of Generation, Transmission and Reception of Electromagnetic Waves  

75. Transmission of Electromagnetic Waves: Accelerating or oscillating charges produce electromagnetic waves. A piece of wire along which charges are made to accelerate is called transmitting antenna. Frequency of waves is the same as that of source. Reception of Electromagnetic Waves: A wire receiving these electromagnetic waves is called receiving antenna. Charges in wire oscillate at the rate of frequency of electromagnetic wave. L - C parallel circuit is used for reception.

76. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

77. Modulation Definition: “The process of mixing the low frequency signal (sound) with high frequency radio waves”. Resultant wave is called modulated wave.

78. Waves in Modulation: Types of Modulation: Amplitude Modulation: Amplitude of carrier wave change. Good for long range. Band width: 540 kHz to 1600 kHz Frequency Modulation: Frequency of carrier wave is changed Good for short range Band width: 88 MHz to 108 MHz

79. Alternating Current A.C Circuit A.C Through A Resistor A.C Through A Capacitor A.C Through An Inductor Impedance R – C And R – L Series Circuits Power In A.C Circuits Series Resonance Circuit Parallel Resonance Circuit Three Phase A.C Supply Principle Of Metal Detectors Choke Electromagnetic Waves Principle Of Generation, Transmission And Reception Of Electromagnetic Waves Modulation ECAT Past Questions

80.     ECAT 2015

81. MCQ: You have 20 inductors available each of 15H. You need an inductor of 1H in a circuit. You achieve it by combination? 15 inductor in parallel 20 inductor in series 15 inductor in series 20 inductor in parallel ECAT 2015

82. MCQ: The relationship between X and Y in the following system Y=x y;’=x Y=x’ Both B & C (insufficient data) ECAT 2015

83. MCQ: Reception of particular radio station is selected by tuning the tuning knob of radio, tuning the tuning knob changes the? Inductance Capacitance Impedance All ECAT 2015

84. MCQ: In amplitude modulation, the amplitude if carrier wave changes in proportion to: The amplitude of the modulating signal The sign of the modulating signal The frequency of the modulating signal All of the above ECAT 2015

85. MCQ: The following device does not use electromagnetic waves for its equation: Ultra sound machine Radar X-Ray machine Mobile phone ECAT 2014

86. MCQ: In frequency modulation, The amplitude of the carrier waves remain same but its frequency changes in proportion to: The amplitude of the modulation signal The sign of the modulation signal The frequency of the modulation signal All of these ECAT 2014

87. MCQ: Reception of a particular radio station is selected by tuning the tuning knob of a radio. Turning the tuning knob changes the: Inductance of the tuning circuit Capacitance of the tuning circuit Resistance of the tuning circuit None of the above ECAT 2014

88. MCQ: In circuit X, L = 5 mH and C = 10 pF are connected in series. In circuit Y, L = 10 mH and C = 5 pF are connected in parallel. The resonance frequency f x and f y of circuits X and Y respectively are related by: f x = 50 f y f x = 0.02 f y f x = f y Cannot be determined ECAT 2013

89. MCQ: When we tune a radio that means: Capacitance change Inductance change Resistance change Frequency change ECAT 2013

90. MCQ: Frequency of A.C mains in Pakistan: 30 Hz 50 Hz 60 Hz 120 Hz ECAT 2012

91. MCQ: Choke is use to: Increase current Decrease voltage Limit current None of these ECAT 2012

92. MCQ: In RC circuit ______ leads the ______ ECAT 2011

93. MCQ: In RLC series circuit, the current at resonance frequency is: Minimum Maximum Zero None ECAT 2011

94. MCQ: In FM, the amplitude of carrier wave is: Diminished Increased Both (A) and (B) None of these ECAT 2011