EdgineerX

1051. A generator converts

A. heat to electrical energy B. electrical energy to mechanical energy C. chemical to electrical energy D. mechanical energy to electrical energy E. light to electrical energy

1052. Self induction in a coil always

A. opposes the change in current B. reverses the current C. stops the current D. assists the change in current E. increases the resistance

1053. A transformer with 500 primary turns and 2500 secondary turns supplying 220 V to the primary gives a secondary voltage of

A. 44 V B. 550 V C. 220 V D. 2500 V E. 1100 V

1054. The peak to peak value of an alternating voltage of peak value V0 is

A. V0/sqrt(2) B. V0/2 C. V0 sqrt(2) D. 2V0 E. V0

1055. A radio receiver is tuned to a station by adjusting the

A. capacitance of the tuning circuit B. resistance in the circuit C. loudspeaker impedance D. aerial length only E. supply voltage

1056. Electrical power is transmitted at high voltage over long distances in order to

A. avoid using transformers B. reduce the voltage at the consumer end directly C. increase the current D. increase the resistance of the line E. reduce the current and hence the I squared R loss

1057. The bulk modulus of a material relates

A. stress to temperature B. strain to time C. volume stress to volume strain D. shear stress to shear strain E. tensile stress to longitudinal strain

1058. A material that can be drawn into thin wires is described as

A. ductile B. amorphous C. malleable D. elastic only E. brittle

1059. Doping a semiconductor with a trivalent impurity produces

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

1060. In a metallic conductor, the valence and conduction bands

A. are both completely full B. overlap or the valence band is partly filled C. have a gap of 1.1 eV D. are both completely empty E. are widely separated

1061. The region near a p-n junction that is free of mobile charge carriers is called the

A. conduction band B. depletion region C. potential well D. channel E. forbidden gap

1062. The peak inverse voltage of a diode is the maximum reverse voltage it can withstand

A. without breaking down B. while conducting C. in forward bias D. during rectification only in a bridge circuit E. at zero current

1063. A bridge rectifier uses

A. a centre tapped transformer and one diode B. three diodes C. two diodes D. one diode E. four diodes

1064. The output of an OR gate is low only when

A. one input is high B. both inputs are high C. the inputs are equal D. both inputs are low E. the inputs differ

1065. A rod moving at high speed along its length appears

A. longer than its rest length B. unchanged in length C. shorter than its rest length D. bent E. of zero length at any speed

1066. The rest mass of a photon is

A. infinite B. zero C. h/c D. equal to that of an electron E. 1.66 x 10^-27 kg

1067. A photocell is a practical device based on

A. the Doppler effect B. pair production C. nuclear fission D. the photoelectric effect E. the Compton effect

1068. The difference between excitation and ionization of an atom is that ionization

A. occurs only in molecules B. requires less energy C. produces no radiation D. involves only the nucleus E. removes the electron completely from the atom

1069. The Paschen series of hydrogen lies in the

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

1070. Stimulated emission differs from spontaneous emission in that the emitted photon is

A. of longer wavelength B. in phase and in the same direction as the incident photon C. emitted in a random direction D. of lower energy E. unpolarized

1071. The relation between the decay constant and the half life is

A. lambda = 2T B. lambda = 1/T2 C. lambda = 0.693/T D. lambda = T E. lambda = T/0.693

1072. In positron emission, the atomic number of the nucleus

A. increases by 2 B. is unchanged C. decreases by 1 D. increases by 1 E. decreases by 4

1073. Control rods in a nuclear reactor are made of materials such as boron or cadmium because they

A. reflect neutrons B. conduct heat well C. slow down neutrons D. produce neutrons E. absorb neutrons strongly

1074. Nuclear fusion requires extremely high temperatures in order to

A. increase the nuclear force range B. reduce the mass defect C. melt the fuel D. overcome the electrostatic repulsion between nuclei E. ionize the surrounding air

1075. Radioisotopes are used in agriculture mainly to

A. trace the uptake of nutrients by plants B. sterilize soil completely C. replace fertilizers D. increase rainfall E. reduce the need for water

Physics