Practice Questions

Q13.Three sound waves of equal amplitudes have frequencies (v −1), v, (v + 1). They superpose to give beats. The number of beats produced per second will be (1) 4 (2) 3 (3) 2 (4) 1

Q16.Two points P and Q are maintained at the potentials of 10 V and −4 V respectively. The work done in moving 100 electrons from P to Q is (1) −19 × 10−17 J (2) 9.60 × 10−17 J (3) −2.24 × 10−16 J (4) 2.24 × 10−16 J

Q25.The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68eV. The work function of the metal is (hc = 1240eVnm) (1) 3.09eV (2) 1.41eV (3) 151eV (4) 1.68eV

Q28.A p-n junction (D) shown in the figure can act as a rectifier. An alternating current source (V ) is connected in the circuit. (1) (2) (3) (4)

Q30.In an experiment the angles are required to be measured using an instrument. 29 divisions of the main scale exactly coincide with the 30 divisions of the vernier scale. If the smallest division of the main scale is half-a- degree (= 0.5∘), then the least count of the instrument is (1) one minute (2) half minute (3) one degree (4) half degree

Q1. The dimension of magnetic field in M, L, T and C (Coulomb) is given as (1) MLT−1C−1 (2) MT2C−2 (3) MT−1C−1 (4) MT−2C−1

Q5. A body of mass m = 3.513 kg is moving along the x-axis with a speed of 5.00 ms−1 . The magnitude of its momentum is recorded as (1) 17.6 kg ms−1 (2) 17.565 kg ms−1 (3) 17.56 kg ms−1 (4) 17.57 kg ms−1

Q8. A planet in a distant solar system is 10 times more massive than the earth and its radius is 10 times smaller. Given that the escape velocity from the earth is 11kms−1 , the escape velocity from the surface of the planet would be (1) 1.1kms−1 (2) 11kms−1 (3) 110kms−1 (4) 0.11kms−1

Q11.A jar filled with two non mixing liquids 1 and 2 having densities ρ1 and ρ2 respectively. A solid ball, made of a material of density ρ3 , is dropped in the jar. It comes to equilibrium in the position shown in the figure. Which JEE Main 2008 JEE Main Previous Year Paper of the following is true for ρ1, ρ2 and ρ3 ? (1) ρ3 < ρ1 < ρ2 (2) ρ1 < ρ3 < ρ2 (3) ρ1 < ρ2 < ρ3 (4) ρ1 < ρ3 < ρ2

Q16.A wave travelling along the x-axis is described by the equation y(x, t) = 0.005 cos(αx −βt). If the wavelength and the time period of the wave are 0.08 m and 2.0 s, respectively, then α and β in appropriate units are (1) α = 25.00π, β = π (2) α = 0.08π , 2.0π (3) α = 0.04π , β = 1.0π (4) α = 12.50π, β = 2.0π

Q17.A thin spherical shell of radius R has charge Q spread uniformly over its surface. Which of the following graphs most closely represents the electric field E(r) produced by the shell in the range 0 ≤r < ∞, where r is the distance from the centre of the shell? (1) (2) (3) (4)

Q22.Relative permittivity and permeability of a material are εr and μr , respectively. Which of the following values of these quantities are allowed for a diamagnetic material? (1) εr = 0.5, μr = 1.5 (2) εr = 1.5, μr = 0.5 (3) εr = 0.5, μr = 0.5 (4) εr = 1.5, μr = 1.5

Q23.A horizontal overhead power line is at a height of 4 m from the ground and carries a current of 100 A from east to west. The magnetic field directly below it on the ground is (μ0 = 4π × 10−7 T m A−1) (1) 2.5 × 10−7 T southward (2) 5 × 10−6 T northward (3) 5 × 10−6 T southward (4) 2.5 × 10−7 northward

Q26.An experiment is performed to find the refractive index of glass using a travelling microscope. In this experiment distance are measured by (1) a vernier scale provided on the microscope (2) a standard laboratory scale (3) a meter scale provided on the microscope (4) a screw gauage provided on the microscope

Q28.Paragraph: Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see in figure). Question: If a strong diffraction peak is observed when electrons are incident at an angle 'i' from the normal to the crystal planes with distance ' d ' between them (see figure), de Broglie wavelength λdB of electrons can be calculated by the relationship ( n is an integer) (1) d sin i = nλdB (2) 2d cos i = nλdB (3) 2d sin i = nλdB (4) d cos i = nλdB

Q34.Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer. The value of the unknown resistor R is JEE Main 2008 JEE Main Previous Year Paper (1) 13.75Ω (2) 220Ω (3) 110Ω (4) 55Ω

Q1. The velocity of a particle is v = v0 + gt + ft2 . If its position is x = 0 at t = 0, then its displacement after unit time (t = 1) is (1) v0 + 2g + 3f (2) v0 + g/2 + f/3 (3) v0 + g + f (4) v0 + g/2 + f

Q2. A particle is projected at 60∘ to the horizontal with a kinetic energy K. The kinetic energy at the highest point is (1) K (2) Zero (3) K/2 (4) K/4

Q10.Angular momentum of the particle rotating with a central force is constant due to (1) Constant Force (2) Constant linear momentum. (3) Zero Torque (4) Constant Torque

Q13.When a system is taken from state i to state f along the path iaf , it is found that Q = 50 cal and W = 20 cal. Along the path' ibf Q = 36 cal. W along the path ibf is (1) 6 cal (2) 16 cal. (3) 66 cal. (4) 14 cal. JEE Main 2007 JEE Main Previous Year Paper

Q14.If Cp and Cv denote the specific heats of nitrogen per unit mass at constant pressure and constant volume respectively, then (1) Cp −Cv = R/28 (2) Cp −Cv = R/14 (3) Cp −Cv = R (4) Cp −Cv = 28R

Q16.A point mass oscillates along the x-axis according to the law x = x0 cos(ωt −π/4). If the acceleration of the particle is written as a = A cos(ωt + δ) (1) A = x0, δ = −π/4 (2) A = x0ω2, δ = −π/4 (3) A = x0ω2, δ = −π/4 (4) A = x0ω2, δ = 3π/4

Q19.A sound absorber attenuates the sound level by 20 dB . The intensity decreases by a factor of (1) 1000 (2) 10000 (3) 10 (4) 100

Q22.The potential at a point x (measured in μm ) due to some charges situated on the x-axis is given by V(x) = 20/ (x2 −4) Volts. The electric field E at x = 4 μm is given by (1) 5/3 Volt/ μm and in the −ve x direction (2) 5/3 Volt/ μm and in the +ve x direction. (3) 10/9 Volt/μm and in the −ve x direction (4) 10/9 Volt/μm and in the +ve x direction.

Q23.If gE and gm are the accelerations due to gravity on the surfaces of the earth and the moon respectively and if Millikan's oil drop experiment could be performed on the two surfaces, one will find the ratio electronic charge on the moon to be electronic charge on the earth (1) 1 (2) 0 (3) gE/gm (4) gm / gE