Practice Questions

Q27.Two spheres of the same material have radii 1 m and 4 m and temperatures 4000 K and 2000 K respectively. The ratio of the energy radiated per second by the first sphere to that by the second is (1) 1 : 1 (2) 16 : 1 (3) 4 : 1 (4) 5 : 3

Q32.At what temperature is the r.m.s. velocity of a hydrogen molecule equal to that of an oxygen molecule at 47∘C ? (1) 80 K (2) 73 K (3) 3 K (4) 20 K Q33.1 mole of a gas with γ = 7/5 is mixed with 1 mole of a gas with γ = 5/3, then the value of γ for the resulting mixture is (1) 7/5 (2) 2/5 (3) 24/16 (4) 12/7 JEE Main 2002 JEE Main Previous Year Paper

Q34.In a simple harmonic oscillator, at the mean position (1) kinetic energy is minimum, potential energy is (2) both kinetic and potential energies are maximum maximum (3) kinetic energy is maximum, potential energy is (4) both kinetic and potential energies are minimum minimum

Q36.A child swinging on a swing in sitting position, stands up, then the time period of the swing will (1) increase (2) decrease (3) remains same (4) increases if the child is tall and decreases if the child is short

Q38.Tube A has both ends open while tube B has one end closed, otherwise they are identical. The ratio of fundamental frequency of tube A and B is (1) 1 : 2 (2) 1 : 4 (3) 2 : 1 (4) 4 : 1

Q39.A tuning fork arrangement (pair) produces 4 beats / sec with one fork of frequency 288cps. A little wax is placed on the unknown fork and it then produces 2 beats /sec. The frequency of the unknown fork is (1) 286 cps (2) 292 cps (3) 294 cps (4) 288 cps

Q40.A wave y = a sin(ωt −kx) on a string meets with another wave producing a node at x = 0. Then the equation of the unknown wave is (1) y = a sin(ωt + kx) (2) y = −a sin(ωt + kx) (3) y = a sin(ωt −kx) (4) y = −a sin(ωt −kx)

Q41.When temperature increases, the frequency of a tuning fork (1) increases (2) decreases (3) remains same (4) increases or decreases depending on the material

Q43.A charged particle q is placed at the centre O of cube of length L (A B C D E F G H). Another same charge q is placed at a distance L from O. Then the electric flux through ABCD is (1) q/4πϵ0L (2) zero (3) q/2πϵ0L (4) q/3πϵ0L

Q44.If a charge q is placed at the centre of the line joining two equal charges Q such that the system is in equilibrium then the value of q is (1) Q/2 (2) −Q/2 (3) Q/4 (4) −Q/4

Q45.If there are n capacitors in parallel connected to V volt source, then the energy stored is equal to (1) CV (2) 12 nCV2 (3) CV2 (4) 2n1 CV 2

Q46.Capacitance (in F ) of a spherical conductor with radius 1 m is (1) 1.1 × 10−10 (2) 10−6 (3) 9 × 10−9 (4) 10−3

Q48.A wire when connected to 220 V mains supply has power dissipation P1 . Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is P2 Then P2 : P1 is (1) 1 (2) 4 (3) 2 (4) 3

Q51. If in the circuit, power dissipation is 150 W, then R is (1) 2Ω (2) 6Ω (3) 5Ω (4) 4Ω JEE Main 2002 JEE Main Previous Year Paper

Q52.If in a circular coil A of radius R, current I is flowing and in another coil B of radius 2R a current 2l is flowing, then the ratio of the magnetic fields BA and BB , produced by them will be (1) 1 (2) 2 (3) 1/2 (4) 4

Q53.If an electron and a proton having same momenta enter perpendicular to a magnetic field, then (1) curved path of electron and proton will be same (2) they will move undeflected (ignoring the sense of revolution) (3) curved path of electron is more curved than that (4) path of proton is more curved of the proton

Q54.Wires 1 and 2 carrying currents i1 and i2 respectively are inclined at an angle θ to each other. What is the force on a small element dl of wire 2 at a distance of r from wire 1 (as shown in the figure) due to the magnetic field of wire 1 ? μ0 (1) θ 2πr i1i2dl tan θ (2) 2πrμ0 i1i2 dl sin (3) 2πr μ0 i1i2dl cos θ (4) 4πrμ0 i1i2dl sin θ

Q56.A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A magnetic induction B constant in time and space, pointing perpendicular and into the plane at the loop exists everywhere with half the loop outside the field, as shown in figure. The induced emf is (1) zero (2) RvB (3) VBL/R (4) VBL

Q59.The power factor of an AC circuit having resistance (R) and inductance (L) connected in series and an angular velocity ω is (1) R/ωL (2) R/(R2 + ω2L2)1/2 (3) ωL/R (4) R/(R2 −ω2L2) 1/2

Q60.In a transformer, number of turns in the primary coil are 140 and that in the secondary coil are 280. If current in primary coil is 4 A, then that in the secondary coil is (1) 4 A (2) 2 A (3) 6 A (4) 10 A

Q62.Infra red radiation is detected by (1) spectrometer (2) pyrometer (3) nanometer (4) photometer

Q63.Which of the following are not electromagnetic waves? (1) cosmic rays (2) gamma rays (3) β-rays (4) X- rays

Q64.An astronomical telescope has a large aperture to (1) reduce spherical aberration (2) have high resolution (3) increase span of observation (4) have low dispersion

Q65.If two mirrors are kept at 60∘ to each other, then the number of images formed by them is (1) 5 (2) 6 (3) 7 (4) 8

Q66.Which of the following is used in optical fibres ? (1) total internal reflection (2) scattering (3) diffraction (4) refraction