EdgineerX

1476. 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

1477. The bulk modulus of a material relates

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

1478. A material that can be drawn into thin wires is described as

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

1479. Doping a semiconductor with a trivalent impurity produces

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

1480. In a metallic conductor, the valence and conduction bands

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

1481. The region near a p-n junction that is free of mobile charge carriers is called the

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

1482. The peak inverse voltage of a diode is the maximum reverse voltage it can withstand

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

1483. A bridge rectifier uses

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

1484. The output of an OR gate is low only when

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

1485. A rod moving at high speed along its length appears

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

1486. The rest mass of a photon is

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

1487. A photocell is a practical device based on

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

1488. The difference between excitation and ionization of an atom is that ionization

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

1489. The Paschen series of hydrogen lies in the

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

1490. Stimulated emission differs from spontaneous emission in that the emitted photon is

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

1491. The relation between the decay constant and the half life is

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

1492. In positron emission, the atomic number of the nucleus

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

1493. Control rods in a nuclear reactor are made of materials such as boron or cadmium because they

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

1494. Nuclear fusion requires extremely high temperatures in order to

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

1495. Radioisotopes are used in agriculture mainly to

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

1496. An error that occurs in the same direction in every reading and does not average out is called

A. a rounding error B. a personal error only C. a random error D. an absolute error E. a systematic error

1497. In multiplication and division, the result is rounded to the

A. smallest number of significant figures among the data B. largest number of significant figures among the data C. number of decimal places in the least precise value D. nearest whole number E. same number of digits as the first value

1498. Dimensional analysis can be used to

A. measure random errors B. determine the direction of a vector C. check the homogeneity of an equation D. find the numerical constant in a formula E. count significant figures

1499. A speed of 72 km per hour is equal to

A. 20 m s-1 B. 7.2 m s-1 C. 25 m s-1 D. 36 m s-1 E. 10 m s-1

1500. The unit vectors i, j and k are directed along

A. the direction of motion only B. the resultant of three vectors C. the x, y and z axes respectively D. any three arbitrary directions E. the field lines

Physics