JEE Advanced 2018 physics questions with solutions

Showing 1–10 of 20 questions

• MCQdifficultGeometrical opticsspherical mirror

  A wire is bent in the shape of a right angled triangle and is placed in front of a concave mirror of focal length f, as shown in the figure. Which of the figures shown in the four options qualitatively represent(s) the shape of the image of the bent wire? (These figures are not to scale.)

  

  Options

  • Option A

    
  • Option B

    
  • Option C

    
  • Option D

    

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• Multi-correctmediumRotational Motionangular momentum in pure rotation and its conservation

  The potential energy of a particle of mass m at distance r from O is V(r)=kr²/2. The particle moves in a circular orbit of radius R. If v is its speed and L its angular momentum about O, which statements are correct?

  Select all that apply

  • Option A

    v = R√[k/(2m)]

  • Option B

    v = R√(k/m)

  • Option C

    L = R²√(mk)

  • Option D

    L = R²√(mk/2)

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• Multi-correcteasyWave Motion

  In an experiment to measure the speed of sound by a resonating air column, a tuning fork of frequency 500 Hz is used. The length of the air column is varied by changing the level of water in the resonance tube. Two successive resonances are heard at air columns of length 50.7 cm and 83.9 cm. Which of the following statements is (are) true ?

  Select all that apply

  • Option A

    The speed of sound determined from this experiment is 332 m s⁻¹

  • Option B

    The end correction in this experiment is 0.9 cm

  • Option C

    The wavelength of the sound wave is 66.4 cm

  • Option D

    The resonance at 50.7 cm corresponds to the fundamental harmonic

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• Multi-correctmediumNuclear physics

  In the decay chain ²³²₉₀Th → ²¹²₈₂Pb, let Nα be the number of α emissions and Nβ the number of β⁻ emissions. Select the correct statement(s).

  Select all that apply

  • Option A

    Nα = 5

  • Option B

    Nα = 6

  • Option C

    Nβ = 2

  • Option D

    Nβ = 4

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• NumericeasyWave Motion

  Two men are walking along a horizontal straight line in the same direction. The man in front walks at a speed 1.0 m s⁻¹ and the man behind walks at a speed 2.0 m s⁻¹. A third man is standing at a height 12m above the same horizontal line such that all three men are in a vertical plane. The two walking men are blowing identical whistles which emit a sound of frequency 1430 Hz. The speed of sound in air is 330 m s⁻¹. At the instant, when the moving men are 10 m apart, the stationary man is equidistant from them. The frequency of beats in Hz, heard by the stationary man at this instant, is __________.

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• ParagraphmediumUnit dimension and error

  If measurement errors in independent quantities are small, a dependent quantity can be expanded to first order. For z=x/y, the relative error is Δz/z = Δx/x + Δy/y; higher-order error terms are neglected.

  Sub-question 1

  For r=(1-a)/(1+a), if the measured dimensionless a has small error Δa, find the error Δr.

  Options

  • Option A

    Δa/(1+a)²

  • Option B

    2Δa/(1+a)²

  • Option C

    2Δa/(1-a²)

  • Option D

    2aΔa/(1-a²)

  Sub-question 2

  In an experiment the initial number of radioactive nuclei is 3000. It is found that 1000 ± 40 nuclei decayed in the first 1.0 s. For |x| << 1, ln (1 + x) = x up to first power in x. The error Δλ, in the determination of the decay constant λ, in s⁻¹, is :-

  Options

  • Option A

    0.04

  • Option B

    0.03

  • Option C

    0.02

  • Option D

    0.01

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• Multi-correctmediumAC Circuits

  In the shown circuit, switches S₁ and S₂ are closed simultaneously at t=0. Both batteries have equal emf V. The current I in the middle wire reaches maximum magnitude Iₘₐₓ at time τ. Select the correct statements.

  

  Select all that apply

  • Option A

    Iₘₐₓ=V/(2R)

  • Option B

    Iₘₐₓ=V/(4R)

  • Option C

    τ=(L/R)ln2

  • Option D

    τ=(2L/R)ln2

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• MatchmediumThermodynamics

  One mole of a monatomic ideal gas undergoes four thermodynamic processes as shown schematically in the PV-diagram below. Among these four processes, one is isobaric, one is isochoric, one is isothermal and one is adiabatic. Match the processes mentioned in List-l with the corresponding statements in List-II.

  

  List 1

  1. P. Process I

  2. Q. Process II

  3. 3. R. Process III

  4. S. Process IV

  List 2

  1. 1. 1. Work done by gas is zero

  2. 2. Temperature remains unchanged

  3. 3. 3. No heat exchanged

  4. 4. 4. Work done by gas is 6P₀V₀

  Options

  • Option A

    P → 4 ; Q → 3 ; R → 1 ; S → 2

  • Option B

    P → 1 ; Q → 3 ; R → 2 ; S → 4

  • Option C

    P → 3 ; Q → 4 ; R → 1 ; S → 2

  • Option D

    P → 3 ; Q → 4 ; R → 2 ; S → 1

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• NumericmediumThermodynamics

  Two conducting cylinders of equal length but different radii are connected in series between two heat baths kept at temperatures T₁ = 300 K and T₂ = 100 K, as shown in the figure. The radius of the bigger cylinder is twice that of the smaller one and the thermal conductivities of the materials of the smaller and the larger cylinders are K₁ and K₂ respectively. If the temperature at the junction of the two cylinders in the steady state is 200 K, then K₁/K₂ is to be determined.

  

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• NumericmediumElectrostaticElectric field intensity

  A particle, of mass 10⁻³ kg and charge 1.0 C, is initially at rest. At time t = 0, the particle comes under the influence of an electric field 𝐄(t) = E₀ sin ωt𝐢 where E₀ = 1.0 N C⁻¹ and ω = 10³ rad s⁻¹. Consider the effect of only the electrical force on the particle. Then the maximum speed, in m s⁻¹, attained by the particle at subsequent times is

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