12th class (Fsc) Physics unit 5 MCQs
51. In case of AC through resistor V and I are:
a. at 180o with each other
b. at 0o with each other
c. at 270o with each other
d. At 90o with each other
52. In three phase A.C supply coils are inclined at an angle of:
a. 120o
b. 0o
c. 180o
d. 90o
53. In three phase voltage across any two lines is about:
a. 400V
b. 220V
c. 430V
d. 230V
54. Direct current cannot flow through:
a. Transistor
b. Inductor
c. Capacitor
d. Resistor
55. The flow of D.C current is opposed by:
a. Capacitor
b. Resistor
c. Inductor
d. All of these
56. In the capacitive circuit of A.C quantity when q=0 the slope of q-r curve is:
a. Zero
b. Maximum
c. Negative
d. Minimum
57. Metal detector consists of:
a. R-C circuit
b. L-C circuit
c. RLC series circuit
d. R-L circuit
58. Choke consumes extremely small:
a. Power
b. Current
c. Potential
d. Charge
59. In case of capacitor the unit of reactance is:
a. Farad
b. Ohm
c. Henry
d. Mho
60. Resistance of choke is:
a. Very small
b. Zero
c. Infinite
d. Large
61. The velocity of an oscillating charge as it moves to and fro along a wire is:
a. Infinite
b. Changing
c. Zero
d. Constant
62. The reactance of capacitor is equal to:
a. C/w
b. wC
c. 1/wC
d. w/C
63. 100µF capacitor is connecting to an AC-voltage of 24V and frequency 50Hz. The reactance of the capacitor is:
a. 34.8Ω
b. 30.8Ω
c. 40Ω
d. 31.8Ω
64. The A.M transmission frequencies range from:
a. 520khZ to 1600KHZ
b. 540KHZ to 1000KHZ
c. 520KHZ to 1400KHZ
d. 540KHZ to 1600khZ
65. Electro-magnetic waves are produced by:
a. Vibrating charge
b. Rest charge
c. Positive charge
d. Moving charge
66. When we accelerate the charges, which type of waves are produced:
a. Stationary waves
b. Mechanical waves
c. Electro-magnetic waves
d. Travelling waves
67. At high frequency the value of reactance of capacitor in A.C circuit will be:
a. Large
b. Small
c. Infinite
d. Zero
68. The range of F.M transmission frequencies is from:
a. 88KHZ to 108KHZ
b. 540KHZ to 1600KHZ
c. 540MHZ to1600MHZ
d. 88KHZ to10.8KHZ
69. In modulation, low frequency signal is known as:
a. Modulated carrier signal
b. Carrier wave
c. Modulation signal
d. Fluctuated signal
70. If the frequency of A.C supplied is doubled then the capacitive reactance becomes:
a. Four times
b. Half
c. One fourth
d. Two time
71. In pure capacitor A.C circuit, the current I and charge q are:
a. Parallel to each other
b. In phase
c. None of above
d. Out of phase
72. An inductor of 1 Henry inductance has a reactance 500 ohms, then the frequency required is approximately:
a. 80 Hz
b. 50 Hz
c. 120 Hz
d. 100 Hz
73. Electro-magnetic waves emitted from radio antenna are:
a. Stationary
b. Longitudinal
c. Transverse
d. Both A and B
74. In a pure inductive A.C circuit the current:
a. In phase with voltage
b. Lags behind voltage by 90o
c. Leads the voltage by 270o
d. Leads the voltage by 90o
75. High frequency radio wave is called as:
a. Matter wave
b. Fluctuative
c. Mechanical wave
d. Carrier wave