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Showing 2826 to 2850 of 3046 questions (page 114 of 122).

2826. The magnetic dipole moment of a coil of N turns, area A, carrying current I is

A. N I A squared B. I A divided by N C. N I divided by A D. N I A E. N A divided by I

2827. Thomson's experiment on the deflection of cathode rays determined the

A. charge to mass ratio of the electron B. mass of the proton C. Planck constant D. charge of the electron E. radius of the atom

2828. A DC generator differs from an AC generator in that it uses

A. no coil B. a capacitor C. a split ring commutator D. no magnet E. slip rings

2829. In an ideal transformer, the quantity that is the same in the primary and secondary is the

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

2830. An induction furnace melts metal by means of

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

2831. The direction of an induced current is such that its magnetic effect

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

2832. In order of increasing wavelength, the correct sequence is

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

2833. A device that converts direct current into alternating current is called

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

2834. An alternating voltage has an rms value of 220 V. Its peak value is about

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

2835. 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

2836. A ferromagnetic material owes its strong magnetism to

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

2837. A transistor used as a switch operates between

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

2838. Besides NAND, the other gate that is universal is

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

2839. A capacitor placed across the output of a rectifier acts as

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

2840. 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

2841. 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. a lower speed D. no charge E. greater mass

2842. The value of Planck's constant is about

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

2843. A major limitation of Bohr's model is that it

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

2844. X-rays are used in industry chiefly for

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

2845. The wavelength of a spectral line is related to the wave number by

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

2846. The radius of a nucleus is of the order of

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

2847. A Geiger Muller counter detects radiation by

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

2848. The most effective general precaution against exposure to ionizing radiation is to

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

2849. 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 large mass of deuterium D. the weak nuclear force E. the absence of neutrons

2850. A radioactive tracer used to study thyroid function is an isotope of

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

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