Practice Questions

Q20.A square frame of side 10 cm and a long straight wire carrying current 1 A are in the plane of the paper. Starting from close to the wire, the frame moves towards the right with a constant speed of 10 m s−1 (see figure). The e.m.f induced at the time the left arm of the frame is at x = 10 cm from the wire is (1) 0.75 μV (2) 1 μV (3) 2 μV (4) 0.5 μV JEE Main 2014 (19 Apr Online) JEE Main Previous Year Paper Q21. → The figure shows a circular area of tthe radius R where a uniform magnetic field B is going into the plane of the paper and increasing in magnitude at a constant rate. In that case, which of the following graphs, drawn schematically, correctly shows the variation of the induced electric field E(r)? (1) (2) (3) (4)

Q20.Three identical bars A, B and C are made of different magnetic materials. When kept in a uniform magnetic field, the field lines around them look as follows: Make the correspondence of these bars with their material being diamagnetic ( D), ferromagnetic (F) and paramagnetic (P) : (1) A ↔D, B ↔P, C ↔F (2) A ↔F, B ↔D, C ↔P (3) A ↔P, B ↔F, C ↔D (4) A ↔F, B ↔P, C ↔D JEE Main 2014 (11 Apr Online) JEE Main Previous Year Paper

Q20.The magnetic field of earth at the equator is approximately 4 × 10−5T. The radius of earth is 6.4 × 106m. Then the dipole moment of the earth will be nearly of the order of : (1) 1020 A m2 (2) 1016 A m2 (3) 1010 A m2 (4) 1023 A m2

Q20.A positive charge ' q ' of mass ' m ' is moving along the +x axis. We wish to apply a uniform magnetic field B for time Δt so that the charge reverses its direction crossing the y axis at a distance d. Then: (1) B = mvqd and Δt = πdv (2) B = 2qdmv and Δt = πd2v (3) B = 2mvqd and Δt = πd2v (4) B = 2mvqd and Δt = πdv

Q21.In the circuit shown here, the point ' C ' is kept connected to point A '' till the current flowing through the circuit becomes constant. Afterward, suddenly, point ' C ' is disconnected from point A '' and connected to point ' B' at time t = 0. Ratio of the voltage across resistance and the inductor at t = RL will be equal to : (1) e (2) 1 1−e (3) - 1 (4) 1−e e

Q21.When the rms voltages VL, VC and VR are measured respectively across the inductor L, the capacitor C and the resistor R in a series LCR circuit connected to an AC source, it is found that the ratio VL : VC : VR = 1 : 2 : 3. If the rms voltage of the AC source is 100 V, then VR is close to : (1) 50 V (2) 70 V (3) 100 V (4) 90 V

Q21.Consider two thin identical conducting wires covered with very thin insulating material. One of the wires is bent into a loop and produces magnetic field B1 , at its centre when a current I passes through it. The ratio B1 : B2 is: (1) 1:1 (2) 1 : 3 (3) 1 : 9 (4) 9 : 1

Q21.Three straight parallel current carrying conductors are shown in the figure. The force experienced by the middle conductor of length 25 cm is: (1) 3 × 10−4 N toward right (2) 6 × 10−4 N toward right (3) 9 × 10−4 N toward right (4) Zero

Q22.If microwaves, X‐ rays, infrared, gamma rays, ultraviolet, radio waves and visible parts of the electromagnetic spectrum are denoted respectively by M , X , I , G , U , R and V the following is the arrangement in ascending order of the wavelength (1) I , M , R, U , V , X and G (2) R, M , I , V , U , X and G (3) M , R, V , X , U , G and I (4) G , X , U , V , I , M and R

Q22.A coil of circular cross-section having 1000 turns and 4 cm2 face area is placed with its axis parallel to a magnetic field which decreases by 10−2 Wb m−2 in 0.01 s. The e.m.f. induced in the coil is: (1) 400mV (2) 200mV (3) 4mV (4) 0.4mV

Q22.During the propagation of electromagnetic wave in a particular medium :- (1) Electric energy density is double of the magnetic (2) Electric energy density is half of the magnetic energy density energy density (3) Electric energy density is equal to the magnetic (4) Both electric and magnetic energy densities are energy density zero

Q22.Match List I (Wavelength range of electromagnetic spectrum) with List II (Method of production of these waves) and select the correct option from the options given below the lists. List I List II 700 nm to (a) (i) Vibration of atoms and molecules. 1 mm 1 nm to Inner shell electrons in atoms moving from one (b) (ii) 400 nm energy level to a lower level. (c) < 10−3 nm (iii) Radioactive decay of the nucleus. (d) 1 mm to 0. 1 m (iv) Magnetron valve. (1) (a) - (iii), (b) - (iv), (c) - (i), (d) - (ii) (2) (a) - (i), (b) - (ii), (c) - (iii), (d) - (iv) (3) (a) - (iv), (b) - (iii), (c) - (ii), (d) - (i) (4) (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i)

Q22.A sinusoidal voltage V(t) = 100 sin(500t) is applied across a pure inductance of L = 0.02H. The current through the coil is: (1) 10 cos(500t) (2) −10 cos(500t) (3) 10 sin(500t) (4) −10 sin(500t)

Q23.The diameter of the objective lens of the microscope makes an angle β at the focus of the microscope. Further, the medium between the object and the lens is the oil of the refractive index n. Then the resolving power of the microscope. JEE Main 2014 (19 Apr Online) JEE Main Previous Year Paper (1) Increases with decreasing value of β (2) Increases with increasing value of n sin 2β (3) Increases with increasing value of 1 (4) Increases with decreasing value of n nsin2β

Q23.Match List - I (Electromagnetic wave type) with List - II (Its association/application) and select the correct option from the choices given below the lists : JEE Main 2014 (06 Apr) JEE Main Previous Year Paper List - I List - II (a) Infrared waves (i) To treat muscular strain (b) Radio waves (ii) For broadcasting (c) X - rays (iii) To detect fracture of bones (d) Ultraviolet rays (iv) Absorbed by the ozone layer of the atmosphere (1) (a) (b) (c) (d) (2) (a) (b) (c) (d) (iv) (iii) (ii) (i) (i) (ii) (iv) (iii) (3) (a) (b) (c) (d) (4) (a) (b) (c) (d) (iii) (ii) (i) (iv) (i) (ii) (iii) (iv)

Q23.A diver looking up through the water sees the outside world contained in a circular horizon. The refractive index of water is 4 , and the diver's eyes are 15 cm below the surface of the water. Then the radius of the circle 3 is : (1) 15×√7 3 cm (2) 15×3√7 cm (3) 15 × 3√7 cm (4) 15 × 3 × √5 cm

Q23.A lamp emits monochromatic green light uniformly in all directions. The lamp is 3% efficient in converting electrical power to electromagnetic waves and consumes 100 W of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of 5 m from the lamp will be nearly: (1) 1.34 V/m (2) 2.68 V/m (3) 4.02 V/m (4) 5.36 V/m

Q23.An electromagnetic wave of frequency 1 × 1014 hertz is propagating along z-axis. The amplitude of electric field is 4 V/m. If ε0 = 8.8 × 10−12C2/N−m2 , then average energy density of electric field will be: (1) 35.2 × 10−10 J/m3 (2) 35.2 × 10−11 J/m3 (3) 35.2 × 10−12 J/m3 (4) 35.2 × 10−13 J/m3

Q24.A thin convex lens made from crown glass (μ = 32 ) has focal length f . When it is measured in two different liquids having refractive indices 4 and 5 , it has the focal lengths f1 and f2 respectively. The correct relation 3 3 between the focal lengths is : (1) f1 = f2 < f (2) f1 > f and f2 becomes negative (3) f2 > f and f1 becomes negative (4) f1 and f2 both become negative

Q24.An object is located in a fixed position in front of a screen. Sharp image is obtained on the screen for two positions of a thin lens separated by 10 cm . The size of the images in two situations are in the ratio 3 : 3. What is the distance between the screen and the object? (1) 124.5 cm (2) 144.5 cm (3) 65.0 cm (4) 99.0 cm

Q24.The focal lengths of objective lens and eye lens of a Galilean Telescope are respectively 30 cm and 3.0 cm. Telescope produces virtual, erect image of an object situated far away from it at least distance of distinct vision from the eye lens. In this condition the Magnifying Power of the Galilean Telescope should be : (1) +8. 8 (2) −11. 2 (3) +11. 2 (4) −8. 8 JEE Main 2014 (09 Apr Online) JEE Main Previous Year Paper

Q24.A ray of light is incident from a denser to a rarer medium. The critical angle for total internal reflection is θiC and Brewster's angle of incidence is θiB , such that sinθiC = η = 1.28 . The relative refractive index of the two sinθiB media is (1) 0.4 (2) 0.2 (3) 0.9 (4) 0.8

Q24.The refractive index of the material of a concave lens is μ. It is immersed in a medium of refractive index μ1 . A parallel beam of light is incident on the lens. The path of the emergent rays when μ1 > μ is: JEE Main 2014 (12 Apr Online) JEE Main Previous Year Paper (1) (2) (3) (4)

Q25.In Young’s double-slit experiment, the distance between the two identical slits is 6. 1 times larger than the slit width. Then the number of intensity maxima observed within the central maximum of the single-slit diffraction pattern is : (1) 3 (2) 6 (3) 24 (4) 12

Q25.Using monochromatic light of wavelength λ, an experimentalist sets up the Young's double slit experiment in three ways as shown. If she observes that y = β′ , the wavelength of light used is : (1) 520 nm (2) 580 nm (3) 540 nm (4) 560 nm