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Showing 2051 to 2075 of 3046 questions (page 83 of 122).

2051. In an ideal transformer, the quantity that is the same in the primary and secondary is the

A. voltage B. current C. resistance D. number of turns E. power

2052. An induction furnace melts metal by means of

A. friction B. chemical reaction C. radiation from a filament D. heat generated by eddy currents induced in the charge E. conduction from a flame

2053. The direction of an induced current is such that its magnetic effect

A. is zero B. reverses the magnet polarity permanently C. is perpendicular to the flux D. assists the flux change producing it E. opposes the flux change producing it

2054. In order of increasing wavelength, the correct sequence is

A. radio waves, visible, X-rays, gamma rays B. gamma rays, X-rays, visible, radio waves C. radio waves, infrared, visible, X-rays D. visible, X-rays, gamma rays, radio waves E. infrared, visible, radio waves, gamma rays

2055. A device that converts direct current into alternating current is called

A. a filter B. a transformer C. an inverter D. an amplifier E. a rectifier

2056. An alternating voltage has an rms value of 220 V. Its peak value is about

A. 110 V B. 156 V C. 440 V D. 311 V E. 220 V

2057. The stress beyond which a material no longer returns to its original shape is the

A. elastic limit B. breaking stress C. ultimate tensile stress D. yield strain E. shear stress

2058. A ferromagnetic material owes its strong magnetism to

A. the alignment of magnetic domains B. lattice vibrations C. nuclear spin D. free electrons only E. its high density

2059. A transistor used as a switch operates between

A. the active region and cut off B. cut off and saturation C. saturation and breakdown D. two active points E. reverse and forward breakdown

2060. Besides NAND, the other gate that is universal is

A. AND B. NOT C. XOR D. OR E. NOR

2061. A capacitor placed across the output of a rectifier acts as

A. a switch B. an amplifier C. a rectifier D. a smoothing filter E. an oscillator

2062. According to special relativity, the mass of a body moving at speed comparable to that of light

A. decreases B. remains unchanged C. increases D. becomes zero E. becomes negative

2063. An electron microscope achieves higher resolution than an optical microscope because electrons have

A. a much shorter de Broglie wavelength B. a larger amplitude C. no charge D. greater mass E. a lower speed

2064. The value of Planck's constant is about

A. 6.63 x 10^-27 J s B. 6.63 x 10^-34 J s C. 9.1 x 10^-31 J s D. 3 x 10^8 J s E. 1.6 x 10^-19 J s

2065. A major limitation of Bohr's model is that it

A. ignores the nucleus B. explains the hydrogen spectrum C. predicts continuous spectra D. cannot account for the spectra of multi-electron atoms or fine structure E. requires quantized angular momentum

2066. X-rays are used in industry chiefly for

A. cooling engines B. welding metals C. generating electricity D. measuring temperature E. detecting flaws and cracks inside castings

2067. The wavelength of a spectral line is related to the wave number by

A. wave number equals h divided by the wavelength B. wave number equals the wavelength C. wave number equals the reciprocal of the wavelength D. wave number equals the wavelength squared E. wave number equals c times the wavelength

2068. The radius of a nucleus is of the order of

A. 10^-6 m B. 10^-10 m C. 10^-15 m D. 10^-3 m E. 10^-20 m

2069. A Geiger Muller counter detects radiation by

A. weighing the sample B. registering the ionization pulse produced in a gas C. photographing the track D. measuring the temperature rise E. measuring the magnetic deflection

2070. The most effective general precaution against exposure to ionizing radiation is to

A. use a stronger source B. increase the exposure time C. hold the source in the hand D. work without monitoring E. maximize the distance and use suitable shielding

2071. Fusion of deuterium nuclei in the laboratory is difficult mainly because of

A. the scarcity of deuterium B. the very high temperature and confinement needed C. the weak nuclear force D. the absence of neutrons E. the large mass of deuterium

2072. A radioactive tracer used to study thyroid function is an isotope of

A. uranium B. cobalt C. carbon D. iodine E. potassium

2073. If 5 g of a product is obtained where 8 g was theoretically possible, the percentage yield is

A. 37.5% B. 80% C. 160% D. 50% E. 62.5%

2074. A gram atom of an element is

A. the mass of one molecule B. one atom of the element C. its atomic number in grams D. always 12 g E. the mass in grams numerically equal to its relative atomic mass

2075. A mass spectrometer separates and detects ions after they have been

A. cooled and condensed B. ionized, accelerated and deflected C. dissolved in water D. precipitated E. burnt in oxygen

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