Practice Questions

Q20.To radiate EM signal of wavelength 𝜆 with high efficiency, the antennas should have a minimum size equal to: (1) 2𝜆 (2) 𝜆 2 (3) 𝜆 (4) 𝜆 4

Q20.A carrier wave of amplitude 15 V is modulated by a sinusoidal base band signal of amplitude 3 V. The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is 3 (1) 2 (2) 2 (3) 1 (4) 5

Q20.A sinusoidal carrier voltage is amplitude modulated. The resultant amplitude modulated wave has maximum and minimum amplitude of 120 V and 80 V respectively. The amplitude of each side band is : (1) 15 V (2) 10 V (3) 20 V (4) 5 V

Q20.By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by 21%? (1) 15% (2) 12% (3) 10% (4) 14%

Q20.The source of time varying magnetic field may be (A) a permanent magnet (B) an electric field changing linearly with time (C) direct current (D) a decelerating charge particle (E) an antenna fed with a digital signal Choose the correct answer from the options given below. (1) (C) and (E) only (2) (D) only (3) (A) only (4) (B) and (D) only

Q20.A current carrying rectangular loop PQRS is made of uniform wire. The length PR = QS = 5 cm and PQ = RS = 100 cm. If ammeter current reading changes from I to 2I , the ratio of : f PQ)2I is: magnetic forces per unit length on the wire PQ due to wire RS in the two cases respectively (f PQI JEE Main 2023 (30 Jan Shift 2) JEE Main Previous Year Paper (1) 1 : 2 (2) 1 : 4 (3) 1 : 5 (4) 1 : 3

Q20.The height of transmitting antenna is 180 m and the height of the receiving antenna is 245 m . The maximum distance between them for satisfactory communication in line of sight will be: (given R = 6400 km ) JEE Main 2023 (15 Apr Shift 1) JEE Main Previous Year Paper (1) 96 km (2) 56 km (3) 48 km (4) 104 km

Q21.In an LC oscillator, if values of inductance and capacitance become twice and eight times, respectively, then the resonant frequency of oscillator becomes x times its initial resonant frequency ω0 . The value of x is: (1) 1/4 (2) 16 (3) 1/16 (4) 4

Q21.An alternating voltage source V = 260 sin(628t) is connected across a pure inductor of 5 mH . Inductive reactance in the circuit is: (1) 3. 14Ω (2) 6. 28Ω (3) 0. 5Ω (4) 0. 318Ω

Q21.As shown in the figure, a long straight conductor with semicircular arc of radius π m is carrying current 10 I = 3A . The magnitude of the magnetic field. at the center O of the arc is: (The permeability of the vacuum = 4π × 10−7 NA−2 ) (1) 6 μT (2) 1 μT (3) 4 μT (4) 3 μT

Q21.For a moving coil galvanometer, the deflection in the coil is 0. 05 rad when a current of 10 mA is passed through it. If the torsional constant of suspension wire is 4. 0 × 10–5 N m rad−1 , the magnetic field is 0. 01 T and the number of turns in the coil is 200 , the area of each turn (in cm2 ) is : (1) 2. 0 (2) 1. 0 (3) 1. 5 (4) 0. 5

Q21.An emf of 0. 08 V is induced in a metal rod of length 10 cm held normal to a uniform magnetic field of 0. 4 T, when move with a velocity of: (1) 0. 5 m s−1 (2) 20 m s−1 (3) 3. 2 m s−1 (4) 2 m s−1

Q21.The speed of a swimmer is 4 km h-1 in still water. If the swimmer makes his strokes normal to the flow of river of width 1 km, he reaches a point 750 m down the stream on the opposite bank. The speed of the river water is ______ km h-1.

Q21.An electron is allowed to move with constant velocity along the axis of current carrying straight solenoid. (A) The electron will experience magnetic force along the axis of the solenoid. (B) The electron will not experience magnetic force. (C) The electron will continue to move along the axis of the solenoid. (D) The electron will be accelerated along the axis of the solenoid. (E) The electron will follow parabolic path-inside the solenoid. Choose the correct answer from the option given below: (1) B, C and D only (2) A and D only (3) B and C only (4) B and E only

Q21.A small particle moves to position 5 ^𝑖- 2 ^𝑗+ ^𝑘 from its initial position 2 ^𝑖+ 3 ^𝑗- 4 ^𝑘 under the action of force 5 ^𝑖+ 2 ^𝑗+ 7 ^𝑘 N. The value of work done will be ______ J.

Q21.A charge particle moving in magnetic field B, has the components of velocity along B as well as perpendicular to B. The path of the charge particle will be (1) helical path with the axis perpendicular to the (2) helical path with the axis along magnetic field B direction of magnetic field B (3) circular path (4) straight along the direction of magnetic field B

Q22.Which of the following Maxwell’s equation is valid for time varying conditions but not valid for static conditions: → → → → (1) (2) ∮ B ⋅ dl = μ0I ∮ E ⋅ dl = 0 −→ → → (3) ∮→D ⋅dA = Q (4) ∮ E ⋅dl = −∂ϕB∂t

Q22.In the given circuit, rms value of current (Irms) through the resistor R is : (1) 2 A (2) 21 A (3) 20 A (4) 2√2 A

Q22.Which of the following are true? A. Speed of light in vacuum is dependent on the direction of propagation. B. Speed of light in a medium is independent of the wavelength of light. C. The speed of light is independent of the motion of the source. D. The speed of light in a medium is independent of intensity. Choose the correct answer from the question given below : (1) A and C only (2) B and D only (3) B and C only (4) C and D only

Q23.In a Young’s double slit experiment, two slits are illuminated with a light of wavelength 800 nm . The line joining A1P is perpendicular to A1A2 as shown in the figure. If the first minimum is detected at P , the value of slits separation a will be : JEE Main 2023 (29 Jan Shift 1) JEE Main Previous Year Paper The distance of screen from slits D = 5 cm . (1) 0. 4 mm (2) 0. 5 mm (3) 0. 2 mm (4) 0. 1 mm

Q23.The ratio of average electric energy density and total average energy density of electromagnetic wave is: (1) 2 (2) 1 (3) 3 (4) 21

Q23.The electric field and magnetic field components of an electromagnetic wave going through vacuum is described by Ex = E0 sin(kz −ωt) By = B0 sin(kz −ωt) Then the correct relation between E0 and B0 is given by (1) E0B0 = ωk (2) E0 = kB0 (3) kE0 = ωB0 (4) ωE0 = kB0

Q23.Match List I and List II List I List II A Microwaves I Physiotherapy B UV rays II Treatment of cancer JEE Main 2023 (31 Jan Shift 2) JEE Main Previous Year Paper C Infra-red rays III Lasik eye surgery D X-rays IV Aircraft navigation Choose the correct answer from the option given below: (1) A-II, B-IV, C-III, D-I (2) A-IV, B-I, C-II, D-III (3) A-IV, B-III, C-I, D-II (4) A-III, B-II, C-I, D-IV

Q23.All electromagnetic wave is transporting energy in the negative z direction. At a certain point and certain time the direction of electric field of the wave is along positive y direction. What will be the direction of the magnetic field of the wave at that point and instant? JEE Main 2023 (25 Jan Shift 1) JEE Main Previous Year Paper (1) Positive direction of x (2) Positive direction of z (3) Negative direction of x (4) Negative direction of y

Q23.A vessel of depth d is half filled with oil of refractive index n1 and the other half is filled with water of refractive index n2. The apparent depth of this vessel when viewed from above will be- (1) 2d(n1+n2) (2) d(n1+n2) n1+n2 2n1n2 (3) dn1n2 (4) dn1n2 2(n1+n2) (n1+n2)