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Showing 2476 to 2500 of 3046 questions (page 100 of 122).

2476. 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

2477. 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

2478. A light emitting diode emits light when it is

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

2479. 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

2480. 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

2481. 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

2482. The energy equivalent of mass m is

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

2483. 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

2484. 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

2485. 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

2486. The work function of a metal is commonly expressed in

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

2487. The Lyman series of hydrogen lies in the

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

2488. 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

2489. 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

2490. The SI unit of radioactive activity is

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

2491. Radiocarbon dating of organic remains uses the isotope

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

2492. 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

2493. 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

2494. Cobalt 60 is used in medicine mainly as a source of

A. beta particles B. alpha particles C. X-rays D. neutrons E. gamma rays for radiotherapy

2495. A radioactive sample of initial activity A0 has a half life T. Its activity after time 4T is

A. A0/4 B. A0/32 C. A0/2 D. A0/16 E. A0/8

2496. The molar mass of carbon dioxide is

A. 28 g mol-1 B. 44 g mol-1 C. 12 g mol-1 D. 32 g mol-1 E. 48 g mol-1

2497. One atomic mass unit is equal to

A. 1.661 x 10^-24 kg B. 9.1 x 10^-31 kg C. 1.6 x 10^-19 kg D. 1.661 x 10^-27 kg E. 6.02 x 10^-23 kg

2498. The total number of atoms in one mole of methane is

A. 1.204 x 10^24 B. 3.01 x 10^24 C. 6.02 x 10^23 D. 5 x 10^23 E. 2.41 x 10^24

2499. The molecular formula of a compound is related to its empirical formula by

A. multiplication by a whole number B. addition of a constant C. the ratio of densities only D. subtraction of hydrogen E. division by a whole number

2500. Percentage yield is calculated as

A. theoretical yield divided by actual yield times 100 B. moles of product times 100 C. actual yield divided by theoretical yield times 100 D. mass of reactants divided by mass of products E. actual yield minus theoretical yield

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