Physics

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76. A Carnot engine works between 500 K and 300 K. Its efficiency is

A. 20% B. 40% C. 60% D. 80% E. 30%

77. In an adiabatic process

A. temperature remains constant B. pressure remains constant C. no heat enters or leaves the system D. volume remains constant E. internal energy remains constant

78. For any spontaneous natural process, the entropy of the universe

A. decreases B. remains constant C. increases D. becomes zero E. becomes negative

79. The value of the Coulomb constant 1/(4 pi epsilon_0) in SI units is about

A. 9 x 10^9 B. 8.85 x 10^-12 C. 6.63 x 10^-34 D. 1.6 x 10^-19 E. 3 x 10^8

80. The electric field intensity inside a hollow charged conductor in electrostatic equilibrium is

A. maximum B. uniform and non-zero C. zero D. infinite E. equal to the surface field

81. The capacitance of a parallel plate capacitor with plate area A and separation d in vacuum is

A. epsilon_0 d / A B. epsilon_0 A / d C. A d / epsilon_0 D. epsilon_0 A d E. d / epsilon_0 A

82. Three capacitors of 3 microfarad each are connected in series. The equivalent capacitance is

A. 9 microfarad B. 3 microfarad C. 1 microfarad D. 0.33 microfarad E. 6 microfarad

83. The energy stored in a capacitor of capacitance C charged to potential difference V is

A. CV B. CV2 C. (1/2)CV2 D. (1/2)CV E. C2V

84. Inserting a dielectric slab between the plates of a capacitor at constant charge

A. increases the potential difference B. decreases the capacitance C. increases the capacitance D. has no effect E. increases the electric field

85. Gauss's law relates the electric flux through a closed surface to

A. the surface area B. the charge enclosed C. the field at the surface only D. the potential at the centre E. the volume enclosed

86. Kirchhoff's first rule is based on the conservation of

A. energy B. charge C. momentum D. mass E. flux

87. A Wheatstone bridge is balanced when

A. R1 R2 = R3 R4 B. R1/R2 = R3/R4 C. R1 + R2 = R3 + R4 D. R1 R3 = R2 R4 E. the galvanometer reads maximum

88. The resistance of a thermistor with a negative temperature coefficient

A. increases with temperature B. decreases with temperature C. is independent of temperature D. becomes zero at 0 K E. varies linearly with current

89. Maximum power is delivered by a cell of emf E and internal resistance r to an external resistance R when

A. R = 0 B. R = r C. R = 2r D. R is infinite E. R = r/2

90. The specific resistance of a conductor depends on

A. its length B. its area of cross section C. its shape D. the nature of the material and temperature E. the current through it

91. Two resistances of 6 ohm and 3 ohm are connected in parallel. The equivalent resistance is

A. 9 ohm B. 4.5 ohm C. 2 ohm D. 18 ohm E. 3 ohm

92. The force on a charge q moving with velocity v at angle theta to a magnetic field B is

A. qvB cos theta B. qvB sin theta C. qvB tan theta D. qv/B E. qB/v

93. The magnetic field inside a long solenoid with n turns per unit length carrying current I is

A. mu_0 I B. mu_0 n I C. mu_0 I / n D. mu_0 n / I E. n I / mu_0

94. The SI unit of magnetic flux is

A. tesla B. weber C. henry D. gauss E. ampere turn

95. A charged particle moving parallel to a uniform magnetic field experiences a force of

A. maximum magnitude B. half the maximum C. zero D. qvB E. qE

96. Ampere's circuital law relates the line integral of the magnetic field around a closed loop to

A. the enclosed charge B. the enclosed current C. the flux through the loop D. the emf induced E. the loop area

97. Lenz's law is a consequence of the conservation of

A. charge B. momentum C. energy D. flux E. mass

98. The motional emf induced in a rod of length l moving with velocity v perpendicular to a magnetic field B is

A. Bvl B. Bv/l C. B/vl D. Bl/v E. B2vl

99. The SI unit of self inductance is

A. weber B. tesla C. henry D. farad E. ohm

100. The energy stored in an inductor of inductance L carrying current I is

A. LI B. LI2 C. (1/2)LI2 D. (1/2)LI E. L/I2

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