JEE Advanced 2020 physics questions with solutions

Showing 1–10 of 26 questions

• MCQmediumWave Optics

  A parallel beam of light strikes a piece of transparent glass having cross section as shown in the figure below. Correct shape of the emergent wavefront will be (figures are schematic and not drawn to scale)-

  

  Options

  • Option A

    
  • Option B

    
  • Option C

    
  • Option D

    

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• NumericmediumThermodynamics

  One mole of helium is initially at pressure P₁ and volume V₁. It expands isothermally to 4V₁, then adiabatically to 32V₁. Let W₁ be the work done during the isothermal part and W₂ the work done during the adiabatic part. If W₁/W₂=f ln 2, find f.

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• NumericmediumFluid Mechanics

  A hot-air balloon of total mass 480 kg floats at 100 m. Its buoyant volume V is constant. After N sandbags of 1 kg each are dropped it floats at 150 m. Air density varies as ρ(h)=ρ₀ exp(-h/h₀), with ρ₀=1.25 kg m⁻³ and h₀=6000 m. Find N.

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• MCQmediumMagnetic effect of current

  A circular coil of radius R and N turns has negligible resistance. As shown in the schematic figure, its two ends are connected to two wires and it is hanging by those wires with its plane being vertical. The wires are connected to a capacitor with charge Q through a switch. The coil is in a horizontal uniform magnetic field Bo parallel to the plane of the coil. When the switch is closed, the capacitor gets discharged through the coil in a very short time. By the time the capacitor is discharged fully, magnitude of the angular momentum gained by the coil will be (assume that the discharge time is so short that the coil has hardly rotated during this time)-

  

  Options

  • Option A

    (π/2)NQB₀R²

  • Option B

    πNQB₀R²

  • Option C

    2πNQB₀R²

  • Option D

    4πNQB₀R²

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• MCQmediumElectromagnetic Induction

  A light aluminium disc is horizontal and free to rotate about its axis. A strong magnet is held vertically above the disc away from its axis. If the magnet is revolved about the disc axis, the disc will:

  

  Options

  • Option A

    rotate in the direction opposite to the direction of magnet's motion

  • Option B

    rotate in the same direction as the direction of magnet's motion

  • Option C

    not rotate and its temperature will remain unchanged

  • Option D

    not rotate but its temperature will slowly rise

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• Multi-correctmediumElectrostatic

  A uniform electric field $\vec{E}$= -400√3 $\hat{j}$ N C⁻¹ exists in a region. A positively charged particle is projected with initial speed 2√10 × 10⁶ m s⁻¹ towards target T as shown. Select the correct statement(s) about the projection angle and time of flight.

  

  Select all that apply

  • Option A

    The particle hits T if projected at 45° from the horizontal.

  • Option B

    The particle hits T if projected at 30° or 60° from the horizontal.

  • Option C

    The time to hit T can be $\sqrt{\frac56}$ μs or $\sqrt{\frac52}$ μs.

  • Option D

    The time to hit T is $\sqrt{\frac53}$μs.

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• MCQmediumElectromagnetic Induction

  A circular coil of radius R and N turns has negligible resistance and hangs vertically. Its ends are connected through a switch to a charged capacitor Q. The coil lies in a horizontal uniform magnetic field B₀ parallel to its plane. When the switch is closed, the capacitor discharges through the coil in a very short time. The angular momentum gained by the coil is:

  

  Options

  • Option A

    (π/2)NQB₀R²

  • Option B

    πNQB₀R²

  • Option C

    2πNQB₀R²

  • Option D

    4πNQB₀R²

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• MCQmediumRotational Motiontorque and rotational equilibrium

  A football of radius R is kept on a hole of radius r (r < R) made on a plank kept horizontally. One end of the plank is now lifted so that it gets tilted making an angle θ from the horizontal as shown in the figure below. The maximum value of θ so that the football does not start rolling down the plank satisfies (figure is schematic and not drawn to scale) -

  

  Options

  • Option A

    sinθ=r/R

  • Option B

    tanθ=r/R

  • Option C

    sinθ=r/2R

  • Option D

    cosθ=r/2R

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• NumericmediumProperties of solid and fluid

  Water is filled slightly above the rim of a glass. Model the excess water as a disc of thickness h with semicircular edges. With ρ = 10³ kg m⁻³, surface tension 0.07 N m⁻¹ and g = 10 m s⁻², find h in mm just before overflow. Image

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• NumericmediumElectrostaticelectric dipole and dipole moment

  A point charge q of mass m is suspended vertically by a string of length λ. A point dipole of dipole moment 𝐩 is now brought towards q from infinity so that the charge moves away. The final equilibrium position of the system including the direction of the dipole, the angles and distances is shown in the figure below. If the work done in bringing the dipole to this position is N × (mgh), where g is the acceleration due to gravity, then the value of N is . (Note that for three coplanar forces keeping a point mass in equilibrium, $\frac{F}{\sin\theta}$ is the same for all forces, where F is any one of the forces and θ is the angle between the other two forces)

  

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