A vertical spring with force constant k is fixed on a table. A b

Subject

Physics

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

The phase difference between the instantaneous velocity and acceleration of a particle executing simple harmonic motion is:

  • 0.5π

  • π

  • 0.707 π

  • 0.707 π

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22.

A vertical spring with force constant k is fixed on a table. A ball of mass m at a height h above the free upper end of the spring falls vertically in the spring. so that the spring is compressed by a distance d. The net work done in the process is:

  • mg space left parenthesis straight h plus straight d right parenthesis space space plus space 1 half space kd squared
  • mg space left parenthesis straight h plus straight d right parenthesis space space minus space 1 half space kd squared
  • mg space left parenthesis straight h minus straight d right parenthesis space space minus space 1 half space kd squared
  • mg space left parenthesis straight h minus straight d right parenthesis space space minus space 1 half space kd squared


B.

mg space left parenthesis straight h plus straight d right parenthesis space space minus space 1 half space kd squared

Work done is equal to change in energy of the body.
The situation is shown in the figure. When mass m falls vertically on spring, then spring si compressed by distance d.

Hence, network done in the process is 

W= Potential energy stored in the spring + Loss of potential energy of mass 


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23.

What is the value of inductance L for which the current is a maximum in a series LCR circuit with C =10μ F and ω = 1000 s-1

  • 100 mH

  • 1 mH

  • cannot bec calculated unless R is known

  • cannot bec calculated unless R is known

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24.

Three point charges +q, - 2q and +q are placed at points (x = 0, y = a, z = 0), (x = 0, y = 0, z = 0) and (x = a, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are :

  • square root of 2 space qa along +y direction
  • square root of 2 qa along the line joining points
    (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)
  • qa along the line joining points

    (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

  • qa along the line joining points

    (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

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25.

The total power dissipated in watts in the circuit shown here is:

  • 16

  • 40

  • 54

  • 54

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26.

The resistance of an ammeter is 13 Ω  and its scale is graduated for a current up to 100 A. After an additional shunt has been connected to this ammeter it becomes possible to measure currents up to 750 A by this meter. The value of shunt resistance is.

  • 20 Ω

  • 2 Ω

  • 0.2 Ω

  • 0.2 Ω

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27.

Under the influence of a uniform magnetic field. a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion.

  • depends on v and not on R

  • depends on both R and v

  • is independent of both R and v

  • is independent of both R and v

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28.

The primary and secondary coil of a transformer have 50 and 1500 turns respectively. If the magnetic flux Φ linked with the primary coil is given Φ = Φo +4t, where Φ is in weber, t is time is second and Φo is a constant the output voltage across the secondary coil is:

  • 90 V

  • 120 V

  • 220 V

  • 220 V

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29.

Two condensers, one of capacity C and the of capacity C/2, are connected to a V volt battery, as shown.



This work done in charging fully both the condensers is:

  • 2 CV2

  • CV2/4

  • 3CV2/4

  • 3CV2/4

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30.

A transforner is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately:



  • 30%

  • 50 %

  • 90 %

  • 90 %

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