Practice Questions

Q11.Two identical strings X and Z made of same material have tension TX and TZ in then if their fundamental frequencies are 450 Hz and 300 Hz, respectively, then the ratio TX/TZ is : (1) 2. 25 (2) 0. 44 (3) 1. 25 (4) 1. 5

Q11.The driver of bus approaching a big wall notices that the frequency of his bus's horn changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall. Find the speed of the bus if speed of the sound is 330 ms–1 : (1) 91 kmh−1 (2) 81 kmh−1 (3) 61 kmh−1 (4) 71 kmh−1

Q11.A potentiometer wire PQ of 1m length is connected to a standard cell E1 . Another cell E2 of emf 1. 02 V is connected with a resistance ' r' and switch S (as shown in figure). With switch S open, the null position is obtained at a distance of 49 cm from Q. The potential gradient in the potentiometer wire is : (1) 0. 02 V/ cm (2) 0. 01 V/ cm (3) 0. 03 V/ cm (4) 0. 04 V/ cm JEE Main 2020 (02 Sep Shift 2) JEE Main Previous Year Paper

Q11.In a building there are 15 bulbs of 45W , 15 bulbs of 100W, 15 small fans of 10W and 2 heaters of 1kW . The voltage of electric main supply is 220V . The minimum fuse capacity (rated value) of the building will be: (1) 5A (2) 25A (3) 15A (4) 20A

Q12.A capacitor C is fully charged with voltage V0 . After disconnecting the voltage source, it is connected in parallel with another uncharged capacitor of capacitance C . The energy loss in the process after the charge is 2 distributed between the two capacitors is : (1) 2 1 CV 02 (2) 13 CV 02 (3) 4 1 CV 02 (4) 16 CV 02

Q12.In the given circuit diagram, a wire is joining points B and D. The current in this wire is: (1) 0.4A (2) 2A (3) 4A (4) zero JEE Main 2020 (09 Jan Shift 1) JEE Main Previous Year Paper

Q12.A capacitor is made of two square plates each of side ‘ a ’ making a very small angle α between them, as shown in figure. The capacitance will be close to: (1) ∈0a2 d (1 −αa2d ) (2) ∈0a2d (1 −αa4d ) (3) ∈0a2 d (1 + αad ) (4) ∈0a2d (1 −3αa2d )

Q12.Consider four conducing materials copper, tungsten, mercury and aluminum with resistivity ρC, ρT, ρM and ρA respectively. Then : (1) ρC > ρA > ρT (2) ρM > ρA > ρC (3) ρA > ρT > ρC (4) ρA > ρM > ρC JEE Main 2020 (02 Sep Shift 1) JEE Main Previous Year Paper

Q12.Effective capacitance of parallel combination of two capacitors C1 and C2 is 10μF. When these capacitors are individually connected to a voltage source of 1V, the energy stored in the capacitor C2 is 4 times that of C1. If these capacitors are connected in series, their effective capacitance will be: (1) 4.2μF (2) 3.2μF (3) 1.6μF (4) 8.4μF

Q12.Two resistors 400 Ω and 800 Ω are connected in series across a 6∨ battery. The potential difference measured by a voltmeter of 10 kΩ across 400 Ω resistor is close to: (1) 2 V (2) 1. 8 V (3) 2. 05 V (4) 1. 95 V

Q12.A parallel plate capacitor has plate of length l, width w and separation of plates is d. It is connected to a battery of emf V . A dielectric slab of the same thickness d and of dielectric constant K = 4 is being inserted between the plates of the capacitor. At what length of the slab inside plates, will the energy stored in the capacitor be two times the initial energy stored? (1) 2l (2) l 3 3 (3) l (4) l 4 2

Q12.A particle of charge q and mass m is moving with a velocity −vˆi(v ≠0) → Y −Z plane at distance d. If there is magnetic field B = B0ˆk, the minimum value of v for which the particle will not hit the screen is : (1) qdB0 (2) 2qdB0 3m m (3) qdB0 (4) qdB0 m 2m

Q12.The figure shows a region of length ' 𝓁 ' with a uniform magnetic field of 0. 3 T in it and a proton entering the region with velocity 4 × 105 m s−1 making an angle 60° with the field. If the proton completes 10 revolution by the time it cross the region shown, ' 𝓁 ' is close to (mass of proton = 1. 67 × 10−27 kg, charge of the proton = 1. 6 × 10−19 C) (1) 0. 11 m (2) 0. 88 m (3) 0. 44 m (4) 0. 22 m

Q12.In the figure, potential difference between A and B is: (1) 10 V (2) 5 V (3) 15 V (4) 0 V

Q12.A long solenoid of radius R carries a time (t) dependent current I(t) = I0t(1 −t) . A ring of radius 2R is placed coaxially near its middle. During the time interval 0 ≤t ≤1, the induced current (IR) and the induced EMF(VR) in the ring change as: (1) Direction of IR remains unchanged and VR is (2) At t = 0.25 direction of IR reverses and VR is maximum at t = 0.5 maximum (3) Direction of IR remains unchanged and VR is (4) At t = 0.5 direction of IR reverses and VR is zero at t = 0.25 zero

Q12.A battery of 3.0 V is connected to a resistor dissipating 0.5 W of power. If the terminal voltage of the battery is 2.5 V, the power dissipated within the internal resistance is: (1) 0.50 W (2) 0.072 W (3) 0.10 W (4) 0.125 W

Q12.Magnitude of magnetic field (in SI units) at the centre of a hexagonal shape coil of side 10 cm, 50 turns and carrying current I (Ampere) in units of μ0Iπ is : (1) 250√3 (2) 50√3 (3) 500√3 (4) 5√3 m s−1 . If an external

Q13.In the figure shown, the current in the 10 V battery is close to : (1) 0. 71 A from positive to negative terminal (2) 0. 42 A from positive to negative terminal (3) 0. 21 A from positive to negative terminal (4) 0. 36 A from negative to postive terminal

Q13.Two capacitors of capacitances C and 2C are charged to potential differences V and 2V , respectively. These are then connected in parallel in such a manner that the positive terminal of one is connected to the negative terminal of the other. The final energy of this configuration is : (1) 256 CV 2 (2) 32 CV 2 (3) zero (4) 92 CV 2

Q13.A wire carrying current I is bent in the shape ABCDEFA as shown, where rectangle ABCDA and ADEFA are perpendicular to each other. If the sides of the rectangles are of lengths a and b, then the magnitude and direction of magnetic moment of the loop ABCDEFA is : abI along + + ˆk ) (2) ˆk ) (1) √2abI along ( √2ˆj √2 ( √2ˆj √2 + + 2ˆk ) (4) ˆk ) (3) √2abI along ( √5ˆj √5 abI along ( √5ˆj √5

Q13.A charged particle carrying charge 1 μC is moving with velocity (2ˆi + 3ˆj + 4ˆk) magnetic field of × 10−3T exists in the region where the particle is moving then the force on (5ˆi + 3ˆj −6ˆk) → → the particle is F × 10−9 N . the vector F is : (1) −0. 30ˆi + 0. 32ˆj −0. 09ˆk (2) −30ˆi + 32ˆj −9ˆk (3) −300ˆi + 320ˆj −90ˆk (4) −3. 0ˆi + 32ˆj −0. 9ˆk

Q13.An electron is moving along +x direction with a velocity of 6 × 106 ms−1 . It enters a region of uniform electric field of 300 V /cm pointing along +y direction. The magnitude and direction of the magnetic field set up in this region such that the electron keeps moving along the x direction will be: (1) 3 × 10−4T, along +z direction (2) 5 × 10−3T, along −z direction (3) 5 × 10−3T, along +z direction (4) 3 × 10−4T, along −zdirection JEE Main 2020 (06 Sep Shift 1) JEE Main Previous Year Paper

Q13.A galvanometer is used in laboratory for detecting the null point in electrical experiments. If, on passing a current of 6mA it produces a deflection of 2° , its figure of merit is close to : (1) 333° A/div (2) 6 × 10−3A/ div (3) 666° A/div. (4) 3 × 10−3A/ div JEE Main 2020 (05 Sep Shift 2) JEE Main Previous Year Paper

Q13.The value of current i1 flowing from A to C in the circuit diagram is : JEE Main 2020 (04 Sep Shift 2) JEE Main Previous Year Paper (1) 5 A (2) 2. 25 A (3) 0. 75 A (4) 1 A

Q13.The length of a potentiometer wire is 1200 cm and it carries a current of 60 mA For a cell of emf 5 V and internal resistance of 20 Ω the null point on it is found to be at 1000 cm The resistance of whole wire is: (1) 80Ω (2) 120Ω (3) 60Ω (4) 100Ω