JEE Mains 2018 physics questions with solutions

Showing 1–10 of 14 questions

• MCQmediumAC Circuits

  For a series RLC circuit driven at resonance angular frequency ω₀, the quality factor Q is:

  Options

  • Option A

    ω₀R/L

  • Option B

    R/(ω₀C)

  • Option C

    CR/ω₀

  • Option D

    ω₀L/R

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• MCQmediumElectromagnetic wave

  An electromagnetic wave enters a non-magnetic medium from air. In air, E⃗₁ = E₀₁ x̂ cos[2πν(z/c - t)]. In the medium, E⃗₂ = E₀₂ x̂ cos[k(2z - ct)], where k and ν are the wave number and frequency in air. If εᵣ₁ and εᵣ₂ are the relative permittivities of air and the medium respectively, which relation is correct?

  Options

  • Option A

    εᵣ₁/εᵣ₂ = 2

  • Option B

    εᵣ₁/εᵣ₂ = 1/4

  • Option C

    εᵣ₁/εᵣ₂ = 1/2

  • Option D

    εᵣ₁/εᵣ₂ = 4

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• MCQmediumAtomic Structure and X-rays

  An electron from the nth excited state of hydrogen emits a photon while returning to the ground state. Let λₙ be the electron de Broglie wavelength in the nth orbit and Λₙ the emitted-photon wavelength. For large n, which relation is correct?

  Options

  • Option A

    Λₙ ≈ A + B/λₙ

  • Option B

    Λₙ² ≈ A + B/λₙ²

  • Option C

    Λₙ² ≈ λₙ

  • Option D

    Λₙ ≈ A + B/λₙ²

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• MCQmediumFluid Mechanics

  A thin tube is bent into a vertical circle of radius r. Equal volumes of immiscible liquids of densities ρ₁ and ρ₂ (ρ₁ > ρ₂) fill half the circle. Find the angle θ between the radius through the common interface and the vertical.

  Options

  • Option A

    tan⁻¹[πρ₁/ρ₂]

  • Option B

    tan⁻¹[(π/2)(ρ₁/ρ₂)]

  • Option C

    tan⁻¹[(π/2)((ρ₁-ρ₂)/(ρ₁+ρ₂))]

  • Option D

    None of these

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• MCQmediumElectrostatic

  Three concentric metal shells A, B and C of respective radii a, b and c (a < b < c) have surface charge densities +σ, -σ and +σ respectively. The potential of shell B is

  Options

  • Option A

    $\frac{\sigma}{\epsilon_{\omicron}}\left\lbrack\frac{a^2-b^2}{b}+c\right\rbrack$

  • Option B

    $\frac{\sigma}{\epsilon_{\omicron}}\left\lbrack\frac{b^2-c^2}{b}+a\right\rbrack$

  • Option C

    $\frac{\sigma}{\epsilon_{\omicron}}\left\lbrack\frac{b^2-c^2}{c}+a\right\rbrack$

  • Option D

    $\frac{\sigma}{\epsilon_{\omicron}}\left\lbrack\frac{a^2-b^2}{a}+c\right\rbrack$

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• MCQmediumUnit dimension and error

  The density of a material in the shape of a cube is determined by measuring three sides of the cube and its mass. If the relative errors in measuring the mass and length are respectively 1.5% and 1%, the maximum error in determining the density is:

  Options

  • Option A

    3.5 %

  • Option B

    4.5 %

  • Option C

    6 %

  • Option D

    2.5 %

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• MCQmediumMagnetic effect of current

  The magnetic dipole moment of a circular loop carrying current I is m and the magnetic field at its centre is B₁. Keeping I constant, the dipole moment is doubled and the new central field is B₂. Find B₁/B₂.

  Options

  • Option A

    √3

  • Option B

    √2

  • Option C

    1/√2

  • Option D

    2

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• MCQmediumAtomic Structure and X-rays

  If the series limit frequency of the Lyman series is vL, then the series limit frequency of the P-fund series is :

  Options

  • Option A

    16 vL

  • Option B

    vL/16

  • Option C

    vL/25

  • Option D

    25 vL

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• MCQmediumSimple Harmonic Motion

  A silver atom in a solid oscillates in simple harmonic motion in some direction with a frequency of 10¹²/s. What is the force constant of the bonds connecting one atom with the other ? (Mole wt. of silver = 108 g and Avagadro number = 6.02 × 10²³ mole-1)

  Options

  • Option A

    2.2 N m⁻¹

  • Option B

    5.5 N m⁻¹

  • Option C

    6.4 N m⁻¹

  • Option D

    7.1 N m⁻¹

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• MCQmediumThermodynamics

  Two moles of an ideal monoatomic gas occupies a volume V at 27°C. The gas expands adiabatically to a volume 2V. Calculate (a) the final temperature of the gas and (b) change in its internal energy.

  Options

  • Option A

    (a) 195 K (b) -2.7 kJ

  • Option B

    (a) 189 K (b) -2.7 kJ

  • Option C

    (a) 195 K (b) 2.7 kJ

  • Option D

    (a) 189 K (b) 2.7 kJ

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