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2251. In an ideal operational amplifier, the input impedance and open loop gain are respectively

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

2252. For a transistor operating as an amplifier, the emitter base junction and collector base junction are

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

2253. Doping silicon with a pentavalent impurity produces

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

2254. According to the special theory of relativity, the speed of light in free space is

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

2255. In the photoelectric effect, the maximum kinetic energy of the emitted electrons is

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

2256. The de Broglie wavelength of a particle of momentum p is

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

2257. The Compton effect demonstrates the

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

2258. 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. equal to hf D. independent of h E. zero

2259. The stopping potential in a photoelectric experiment depends on

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

2260. According to Bohr's theory, the angular momentum of an electron in the nth orbit is

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

2261. The spectral series of hydrogen that lies in the visible region is the

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

2262. The ionization energy of a hydrogen atom in its ground state is

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

2263. Laser action requires

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

2264. The continuous part of an X-ray spectrum is produced by

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

2265. The radius of the nth Bohr orbit in hydrogen is proportional to

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

2266. Isotopes of an element have the same

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

2267. A radioactive sample has a half life of 10 days. The fraction remaining after 30 days is

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

2268. In beta minus decay, the atomic number of the nucleus

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

2269. The energy released in nuclear reactions arises from

A. chemical bonding B. electron transitions C. frictional heating D. mass defect E. ionization

2270. Energy production in the Sun is mainly due to

A. gravitational contraction alone B. chemical combustion C. nuclear fusion D. nuclear fission E. radioactive decay of uranium

2271. Which radiation has the greatest penetrating power?

A. proton B. gamma C. beta D. neutron in air only E. alpha

2272. In a nuclear reactor, the moderator is used to

A. slow down fast neutrons B. shield the operators C. absorb excess neutrons D. control the coolant flow E. increase the fuel temperature

2273. The value of Avogadro's number is

A. 3.01 x 10^23 B. 1.66 x 10^-24 C. 6.02 x 10^23 D. 6.02 x 10^24 E. 6.02 x 10^22

2274. The molar volume of an ideal gas at standard temperature and pressure is

A. 1 dm3 B. 11.2 dm3 C. 24 dm3 D. 22.414 dm3 E. 44.8 dm3

2275. The reactant that is completely consumed first and therefore limits the amount of product is called the

A. catalyst B. limiting reactant C. excess reactant D. intermediate E. spectator species

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