JEE Mains 2015 physics questions with solutions

Showing 1–10 of 15 questions

• MCQmediumProperties of solid and fluid

  Two closely spaced glass plates have water between them. The side water surface is approximately cylindrical with radius R. If the surface tension is T, by how much is the water pressure below atmospheric pressure? Image

  Options

  • Option A

    T/(4R)

  • Option B

    T/(2R)

  • Option C

    4T/R

  • Option D

    2T/R

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• MCQmediumElectromagnetic wave

  A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is:

  Options

  • Option A

    5.48 V/m

  • Option B

    7.75 V/m

  • Option C

    1.73 V/m

  • Option D

    2.45 V/m

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• MCQmediumCapacitor

  In the given circuit, charge Q₂ on the 2µF capacitor changes as C is varied from 1µF to 3µF. Q₂ as a function of 'C' is given properly by : (figures are drawn schematically and are not to scale):

  

  Options

  • Option A

    
  • Option B

    
  • Option C

    
  • Option D

    

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• MCQmediumAC Circuits

  An LCR circuit is equivalent to a damped oscillator. The capacitor is initially charged to Q₀ and then connected to L and R. For two inductances L₁>L₂, which graph correctly shows Qₘₐₓ² versus time?

  

  Options

  • Option A

    
  • Option B

    
  • Option C

    
  • Option D

    

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• MCQmediumCapacitor

  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 30 m from it, would equal :

  

  Options

  • Option A

    480 N/C

  • Option B

    240 N/C

  • Option C

    360 N/C

  • Option D

    420 N/C

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• MCQmediumGravitationGravitation, Gravitational Field & Potential Energy

  A spherical cavity of radius R/2 is removed from a uniform solid sphere of mass M and radius R, as shown. The cavity is internally tangent to the original surface. Taking V = 0 at infinity, find the gravitational potential at the centre of the cavity.

  

  Options

  • Option A

    -2GM/(3R)

  • Option B

    -2GM/R

  • Option C

    -GM/(2R)

  • Option D

    -GM/R

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• MCQmediumAtomic Structure and X-rays

  As an electron makes a transition from an excited state to the ground state of a hydrogen - like atom/ion :

  Options

  • Option A

    kinetic energy decreases, potential energy increases but total energy remains same

  • Option B

    kinetic energy and total energy decrease but potential energy increases

  • Option C

    its kinetic energy increases but potential energy and total energy decreases

  • Option D

    kinetic energy, potential energy and total energy decrease

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• MCQmediumThermodynamics

  Consider a spherical shell of radius R at temperature T. Black-body radiation inside it behaves as a photon gas with energy density U/V proportional to T⁴ and pressure p=U/(3V). If the shell undergoes adiabatic expansion, which relation between T and R is correct?

  Options

  • Option A

    T∝1/R

  • Option B

    T∝1/R³

  • Option C

    T∝ $e^{-R}$

  • Option D

    T∝ $e^{-3R}$

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• MCQmediumMagnetic effect of current

  Two coaxial solenoids of different radii carry current I in the same direction. Let F⃗₁ be the magnetic force on the inner solenoid due to the outer one and F⃗₂ the magnetic force on the outer solenoid due to the inner one. Then:

  Options

  • Option A

    F⃗₁ is radially inward and F⃗₂=0

  • Option B

    F⃗₁ is radially outward and F⃗₂=0

  • Option C

    F⃗₁=F⃗₂=0

  • Option D

    F⃗₁ is radially inward and F⃗₂ is radially outward

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• MCQmediumMagnetic effect of current

  Two long thin parallel wires carry equal current I and are suspended by insulating threads of length L, each thread making angle θ with the vertical as shown. If the mass per unit length of each wire is λ, find I.

  

  Options

  • Option A

    2√(πgL/μ₀) tanθ

  • Option B

    √(πλgL/μ₀) tanθ

  • Option C

    sinθ·√[πλgL/(μ₀ cosθ)]

  • Option D

    2sinθ·√[πλgL/(μ₀ cosθ)]

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