JEE Mains 2018 physics questions with solutions

Showing 1–10 of 14 questions

• MCQmediumCurrent electricityElectrical Instruments: Galvanometer, Ammeter, Voltmeter & Potentiometer

  In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across 52cm of the potentiometer wire. If the cell is shunted by resistance of 5 Ω, a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.

  Options

  • Option A

    2 Ω

  • Option B

    2.5 Ω

  • Option C

    1 Ω

  • Option D

    1.5 Ω

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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 %

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• MCQmediumCapacitor

  A parallel-plate capacitor of capacitance 90 pF is connected to a 20 V battery. A dielectric of dielectric constant K = 5/3 is inserted between the plates. Find the magnitude of the induced charge.

  Options

  • Option A

    0.3 nC

  • Option B

    2.4 nC

  • Option C

    0.9 nC

  • Option D

    1.2 nC

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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

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

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →
• 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

  Check answerShow answer

  JEE Mains 2018

  Open question & full solution →