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Showing 1376 to 1400 of 1648 questions (page 56 of 66).

1376. The average value of a sinusoidal alternating current over one complete cycle is

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

1377. The frequency of the domestic AC mains supply in Pakistan is

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

1378. At resonance in a series RLC circuit, the impedance is

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

1379. In a purely capacitive AC circuit, the current

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

1380. 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

1381. At absolute zero, a pure intrinsic semiconductor behaves as

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

1382. A paramagnetic substance placed in a magnetic field is

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

1383. The output ripple frequency of a half wave rectifier fed from a 50 Hz supply is

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

1384. A photodiode used as a light detector is normally operated in

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

1385. A light emitting diode emits light when it is

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

1386. The output of an XOR gate is high when

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

1387. In a common emitter transistor amplifier, the current gain beta is the ratio of

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

1388. According to special relativity, a moving clock runs

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

1389. The energy equivalent of mass m is

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

1390. 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

1391. The wave nature of electrons was confirmed experimentally by

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

1392. The momentum of a photon of wavelength lambda is

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

1393. The work function of a metal is commonly expressed in

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

1394. The Lyman series of hydrogen lies in the

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

1395. The energy of the electron in the second Bohr orbit of hydrogen is

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

1396. In alpha decay, the mass number and atomic number of the nucleus change by

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

1397. The SI unit of radioactive activity is

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

1398. Radiocarbon dating of organic remains uses the isotope

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

1399. Nuclear forces are

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

1400. The minimum mass of fissile material required to sustain a chain reaction is called the

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

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