310 J of heat is required to raise the temperature of 2 moles of

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

The dimensional formula for impulse is

  • [MLT-1]

  • [ML-1T]

  • [M-1LT-1]

  • [ML-1T-1]


2.

The maximum height attained by a projectile when thrown at an angle θ with the horizontal is found to be half the horizontal range. Then θ is equal to

  • tan-1 (2)

  • π6

  • π4

  • tan-1 12


3.

A shell of mass 20 kg at rest explodes into two fragments whose masses are in the ratio 2 : 3. The smaller fragment moves with a velocity of 6 ms-1. The kinetic energy of the larger fragment is

  • 96 J

  • 216 J

  • 144 J

  • 360 J


4.

The acceleration due to gravity becomes g2 (g = acceleration due to gravity on the surface of the earth) at a height equal to

  • 4R

  • R4

  • 2R

  • R2


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5.

Water rises in plant fibres due to

  • capillarity

  • viscosity

  • fluid pressure

  • osmosis


6.

The cylindrical tube of a spray pump has a cross-section of 8 cm2, one end of which has 40 fine holes each of area 10-8 m2. Ifthe liquid flows inside the tube with a speed of 0.15 m min-1 the speed with which the liquid is ejected through the holes is

  • 50 ms-1

  • 5 ms-1

  • 0.05 ms-1

  • 0.5 ms-1


7.

During an adiabatic process, the cube of the pressure is found to be inversely proportional to the fourth power of the volume. Then the ratio of specific heats is

  • 1

  • 1.33

  • 1.67

  • 1.4


8.

Two identical rods AC and CB made of two different metals having thermal conductivities in the ratio 2 : 3 are kept in contact with each other at the end C as shown in the figure. A is at 100°C and B is at 25°C. Then the junction C is at

               

  • 55°C

  • 60°C

  • 75°C

  • 50°C


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9.

310 J of heat is required to raise the temperature of 2 moles of an ideal gas at constant pressure from 25°C to 35°C. The amount of heat required to raise the temperature of the gas through the same range at constant volume is

  • 384 J

  • 144 J

  • 276 J

  • 452 J


B.

144 J

At constant pressure,

Heat required = nCpΔT

⇒            310 = 2 × Cp × (35 − 25)

⇒              Cp = 31020 = 15.5 J/mol/K

Similarly, at constant volume,

Heat required = nCVΔT

                     = 2 (Cp − R) × (35 − 25)    [Cp − CV = R]

                     = 2 × (15.5 − 8.30) × 10

                     = 2 × 7.2 × 10 

                     = 144 J


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10.

A Carnot's engine operates with source at 127°C and sink at 27°C. If the source supplies 40 kJ of heat energy, the work done by the engine is

  • 30 kJ

  • 10 kJ

  • 4 kJ

  • 1 kJ


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