Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

‘n’ moles of an ideal gas undergoes a process A→B as shown in the figure. The maximum temperature of the gas during the process will be:

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12.

A particle performs simple harmonic motion with amplitude A. It's speed is trebled at the instant that it is at a distance 2A/3 from the equilibrium position. The new amplitude of the motion is:

  • straight A over 3 square root of 41
  • 3A

  • straight A square root of 3
  • straight A square root of 3
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13.

The region between two concentric spheres of radii ‘a’ and ‘b’, respectively (see figure), has volume charge density ρ = A/r , where A is a constant and r is the distance from the centre. At the centre of the spheres is a point charge Q. The value of A such that the electric field in the region between the spheres will be constant is:

  • fraction numerator straight Q over denominator 2 πa squared end fraction
  • fraction numerator straight Q over denominator 2 straight pi left parenthesis straight b to the power of 2 minus end exponent straight a squared right parenthesis end fraction
  • fraction numerator 2 straight Q over denominator straight pi left parenthesis straight a squared minus straight b squared right parenthesis end fraction
  • fraction numerator 2 straight Q over denominator straight pi left parenthesis straight a squared minus straight b squared right parenthesis end fraction


A.

fraction numerator straight Q over denominator 2 πa squared end fraction

A Gaussian surface at distance r from centre.




fraction numerator straight Q space plus integral subscript straight a superscript straight r begin display style straight A over straight r end style 4 straight pi squared dr over denominator straight epsilon subscript straight o end fraction space equals space straight E 4 πr squared
straight E 4 straight epsilon subscript straight o straight r squared space equals space straight Q space plus space straight A fraction numerator 4 straight pi over denominator straight r squared end fraction open parentheses fraction numerator straight r squared minus straight a squared over denominator 2 end fraction close parentheses
straight E space equals fraction numerator 1 over denominator 4 πε subscript straight o end fraction space open square brackets straight Q over straight r squared plus straight A space 2 straight pi open parentheses fraction numerator straight r squared minus straight a squared over denominator straight r squared end fraction close parentheses close square brackets
straight E space equals space fraction numerator 1 over denominator 4 πε subscript straight o end fraction open square brackets straight Q over straight r squared plus straight A 2 straight pi minus fraction numerator straight A 2 πa squared over denominator straight r squared end fraction close square brackets
straight E space equals space fraction numerator 1 over denominator 4 πε subscript straight o end fraction space straight x space straight A space straight x space 2 straight pi
At the centre of the sphere is a point charge Q. The value of A such that the electric field in the region between the spheres will be constant is 
As, Q = 2πAa2
i.e A = Q/2πa2

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14.

A combination of capacitors is set up as shown in the figure. The magnitude of the electric field, due to a point charge Q (having a charge equal to the sum of the charges on the 4 µF and 9 µF capacitors), at a point distant 30 m from it, would equal:


  • 240N/C

  • 360N/C

  • 420N/C

  • 420N/C

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15.

Two identical wires A and B, each of length ‘l’, carry the same current I. Wire A is bent into a circle of radius R and wire B is bent to form a square of side ‘a’. If BA and BB are the values of the magnetic field at the centres of the circle and square respectively, then the ratio BA /BB is:

  • straight pi squared over 8
  • fraction numerator straight pi squared over denominator 16 square root of 2 end fraction
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16.

Hysteresis loops for two magnetic materials A and B are given below:



These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use:

  • A for electric generators and transformers.

  • A for electromagnets and B for electric generators

  • A for transformers and B for electric generators.

  • A for transformers and B for electric generators.

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17.

An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms), 50 Hz AC supply, the series inductor needed for it to work is close to:

  • 80 H

  • 0.08 H

  • 0.044 H

  • 0.044 H

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18.

A galvanometer having a coil resistance of 100 Ω gives a full-scale deflection, when a current of 1 mA is passed through it. The value of the resistance, which can convert this galvanometer into ammeter giving a full-scale deflection for a current of 10 A, is:

  • 0.01 Ω

  • 2 Ω

  • 0.1 Ω

  • 0.1 Ω

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19.

The temperature dependence of resistances of Cu and undoped Si in the temperature range 300-400 K is best described by:

  • Linear increase for Cu, linear increase for Si.

  • Linear increase for Cu, exponential increase for Si.

  • Linear increase for Cu, exponential decrease for Si.

  • Linear increase for Cu, exponential decrease for Si.

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20.

Arrange the following electromagnetic radiations per quantum in the order of increasing energy:

A: Blue light
B: Yellow light
C: X-ray
D: Radiowave

  • D, B, A, C

  • A, B, D, C

  • C, A, B, D

  • C, A, B, D

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