40. The maximum efficiency of a heat engine which operates between the measured
temperatures of 227 °C and 727 °C is
A. 50 %
B. 20 %
C. 30 %
D. 40 %

41. The stopping potential for electrons ejected by 14 6.8×10 Hz electromagnetic radiation
incident on a certain sample is 1.8V. The kinetic energy of the most energetic electrons
ejected and the work function of the sample, respectively, are
A. 1.8eV, 2.8eV
B. 1.8eV, 1.0eV
C. 1.8eV, 4.6eV
D. 2.8eV, 1.0eV.

42. When a kaon decays via the strong interaction the products must include a:
A. baryon
B. lepton
C. strange particle
D. electron

43. A particle with spin angular momentum is called a:
A. lepton
B. hadron
C. fermion
D. boson.

44. Which of the following consists entirely of vector quantities?
A. velocity, magnetic flux and reaction
B. tension, magnetic flux and mass
C. displacement, impulse and power
D. work, pressure and moment
45. Two forces each of 10N act on a body, one towards the north and the other towards the
east. The magnitude and the direction of the resultant force are
A. 10N, 45oW
B. 20N, 45oE
C. 10 2 N, 45oW
D. 10 2 N, 45oE

46. The main reason for making the cover of a vacuum flask air tight is to prevent heat loss
by
A. conduction
B. evaporation
C. radiation
D. convection

47. A cell can supply currents of 0.4A and 0.2A through a 4.0Ω and 10.0Ω resistors
respectively. The internal resistance to the cell is
A. 0.5Ω
B. 1.0Ω
C. 1.5Ω
D. 2.0Ω

48. A working electric motor takes a current of 1.5A when the p.d. across it is 250V.
if its efficiency is 80%, the power output is
A. 562.0W
B. 469.0W
C. 300.0W
D. 133.0W

49. At what frequency would a capacitor of 2.5µF used in radio circuit have a reactance of
250Ω?
A. 200π Hz
B.800π Hz
C.π800 Hz
D. 8000π Hz

50. A certain radioactive source emits radiations that were found to de deflected by both
magnetic and electric fields. The radiations are
A. ultra-violet rays
B. gamma rays
C. alpha rays
D. beta rays

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