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Showing 826 to 850 of 3046 questions (page 34 of 122).

826. In an insulator, the energy gap between the valence and conduction bands is

A. negative B. about 0.7 eV C. about 1.1 eV D. zero E. greater than about 5 eV

827. Above the Curie temperature, a ferromagnetic material becomes

A. superconducting B. more strongly ferromagnetic C. diamagnetic D. non-magnetic in the sense of losing all response E. paramagnetic

828. Stress within the elastic limit is

A. zero B. inversely proportional to strain C. directly proportional to strain D. independent of strain E. proportional to the square of strain

829. A p-n junction diode conducts appreciably when

A. reverse biased B. forward biased C. at absolute zero D. unbiased E. the depletion region widens

830. The output ripple frequency of a full wave rectifier fed from a 50 Hz supply is

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

831. A Zener diode in a voltage regulator circuit is operated in

A. forward bias B. the cut off region C. zero bias D. reverse bias beyond the breakdown voltage E. the saturation region

832. Which logic gate is called a universal gate?

A. OR B. NAND C. AND D. NOT E. XOR

833. In an ideal operational amplifier, the input impedance and open loop gain are respectively

A. zero and infinite B. infinite and zero C. infinite and infinite D. finite and unity E. zero and zero

834. For a transistor operating as an amplifier, the emitter base junction and collector base junction are

A. both reverse biased B. unbiased C. both forward biased D. reverse and forward biased respectively E. forward and reverse biased respectively

835. Doping silicon with a pentavalent impurity produces

A. an n-type semiconductor B. a superconductor C. an intrinsic semiconductor D. an insulator E. a p-type semiconductor

836. According to the special theory of relativity, the speed of light in free space is

A. dependent on the observer velocity B. infinite C. different for different observers D. the same for all inertial observers E. dependent on the source velocity

837. In the photoelectric effect, the maximum kinetic energy of the emitted electrons is

A. hf B. hf + work function C. hf - work function D. independent of frequency E. work function - hf

838. The de Broglie wavelength of a particle of momentum p is

A. h/p B. h/p2 C. p/h D. h p2 E. hp

839. The Compton effect demonstrates the

A. polarization of X-rays B. wave nature of light C. transverse nature of light D. particle nature of light E. interference of X-rays

840. Heisenberg's uncertainty principle states that the product of the uncertainties in position and momentum is

A. at most h B. at least of the order of h/(4 pi) C. zero D. equal to hf E. independent of h

841. The stopping potential in a photoelectric experiment depends on

A. the area of the cathode B. the intensity of light only C. the distance of the source D. the frequency of light and the material E. the polarization of light

842. According to Bohr's theory, the angular momentum of an electron in the nth orbit is

A. n2 h B. nh/(2 pi) C. h/n D. nh E. h/(2 pi n)

843. The spectral series of hydrogen that lies in the visible region is the

A. Brackett series B. Pfund series C. Balmer series D. Lyman series E. Paschen series

844. The ionization energy of a hydrogen atom in its ground state is

A. 1.51 eV B. 10.2 eV C. 3.4 eV D. 27.2 eV E. 13.6 eV

845. Laser action requires

A. population inversion B. thermal equilibrium C. incoherent sources D. a very low pumping rate E. a single energy level

846. The continuous part of an X-ray spectrum is produced by

A. nuclear decay B. deceleration of fast electrons in the target C. electron transitions between inner shells D. thermal emission from the filament E. stimulated emission

847. The radius of the nth Bohr orbit in hydrogen is proportional to

A. n2 B. n C. 1/n2 D. n3 E. 1/n

848. Isotopes of an element have the same

A. number of neutrons B. mass number C. atomic mass D. atomic number E. binding energy

849. A radioactive sample has a half life of 10 days. The fraction remaining after 30 days is

A. 1/4 B. 1/3 C. 1/16 D. 1/2 E. 1/8

850. In beta minus decay, the atomic number of the nucleus

A. remains unchanged B. decreases by 2 C. increases by 1 D. increases by 2 E. decreases by 1

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