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Showing 1051 to 1075 of 3046 questions (page 43 of 122).

1051. The average value of a sinusoidal alternating current over one complete cycle is

A. the peak value B. twice the peak value C. zero D. 0.707 times the peak value E. 0.637 times the peak value

1052. The frequency of the domestic AC mains supply in Pakistan is

A. 60 Hz B. 50 Hz C. 100 Hz D. 25 Hz E. 220 Hz

1053. At resonance in a series RLC circuit, the impedance is

A. minimum and equal to R B. maximum and equal to XL C. equal to XC D. zero E. infinite

1054. In a purely capacitive AC circuit, the current

A. leads by 180 degrees B. lags the voltage by 90 degrees C. is in phase with the voltage D. leads the voltage by 90 degrees E. is zero

1055. The modulus that describes the deformation produced by a tangential force is

A. bulk modulus B. shear modulus C. Young's modulus D. compressibility E. Poisson's ratio

1056. At absolute zero, a pure intrinsic semiconductor behaves as

A. a superconductor B. a metal C. a conductor D. a p-type material E. an insulator

1057. A paramagnetic substance placed in a magnetic field is

A. permanently magnetized B. strongly repelled C. weakly attracted D. unaffected E. strongly attracted

1058. The output ripple frequency of a half wave rectifier fed from a 50 Hz supply is

A. 25 Hz B. zero C. 100 Hz D. 150 Hz E. 50 Hz

1059. A photodiode used as a light detector is normally operated in

A. breakdown as a regulator B. forward bias C. zero bias only D. reverse bias E. the saturation region of a transistor

1060. A light emitting diode emits light when it is

A. unbiased B. forward biased C. reverse biased D. in breakdown E. cooled

1061. The output of an XOR gate is high when

A. the inputs are different B. both inputs are high C. either input is low D. both inputs are low E. the inputs are the same

1062. In a common emitter transistor amplifier, the current gain beta is the ratio of

A. collector current to base current B. collector current to emitter current C. collector voltage to base voltage D. base current to collector current E. emitter current to base current

1063. According to special relativity, a moving clock runs

A. at the same rate B. only at the speed of light C. slower than a stationary clock D. faster than a stationary clock E. backwards

1064. The energy equivalent of mass m is

A. mc B. mc2 C. (1/2)mc2 D. m/c2 E. m2c

1065. Photoemission does not occur if the incident light has a frequency below the

A. stopping potential B. Rydberg frequency C. Compton frequency D. threshold frequency E. cut off wavelength

1066. The wave nature of electrons was confirmed experimentally by

A. Millikan's oil drop experiment B. Michelson's interferometer C. the photoelectric experiment D. Rutherford's scattering experiment E. the Davisson and Germer electron diffraction experiment

1067. The momentum of a photon of wavelength lambda is

A. h lambda B. hc/lambda C. h/lambda D. lambda/h E. h/c lambda

1068. The work function of a metal is commonly expressed in

A. electron volts B. watts C. coulombs D. joules only E. hertz

1069. The Lyman series of hydrogen lies in the

A. infrared region B. visible region C. microwave region D. X-ray region E. ultraviolet region

1070. The energy of the electron in the second Bohr orbit of hydrogen is

A. -0.85 eV B. -6.8 eV C. -1.51 eV D. -3.4 eV E. -13.6 eV

1071. In alpha decay, the mass number and atomic number of the nucleus change by

A. -4 and -2 B. -2 and -4 C. -1 and 0 D. -4 and +2 E. 0 and -1

1072. The SI unit of radioactive activity is

A. roentgen B. becquerel C. curie D. gray E. sievert

1073. Radiocarbon dating of organic remains uses the isotope

A. uranium 238 B. carbon 12 C. potassium 40 D. carbon 13 E. carbon 14

1074. Nuclear forces are

A. short range and charge independent B. long range and charge dependent C. effective only between protons D. weaker than gravitational forces E. identical to electrostatic forces

1075. The minimum mass of fissile material required to sustain a chain reaction is called the

A. binding mass B. mass defect C. critical mass D. threshold mass E. atomic mass

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