Practice Questions

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.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

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.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 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.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

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.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.Which of the following will NOT be observed when a multimeter (operating in resistance measuring mode) probes connected across a component, are just reversed? JEE Main 2020 (03 Sep Shift 2) JEE Main Previous Year Paper (1) Multimeter shows an equal deflection in both (2) Multimeter shows NO deflection in both cases cases i.e., before and after reversing the probes if i.e. before and after reversing the probes if the the chosen component is resistor. chosen component is capacitor (3) Multimeter shows a deflection, accompanied by a (4) Multimeter shows NO deflection in both cases splash of light out of connected component in i.e. before and after reversing the probes is the one direction and NO deflection on reversing the chsosen component is metal wire. probes if the chosen component is LED

Q13.A beam of protons with speed 4 × 105 m s−1 enters a uniform magnetic field of 0. 3 T at an angle 60° to the magnetic field, the pitch of the resulting helical path of protons is close to : (Mass of the proton = 1. 67 × 10−27 kg, charge of the proton = 1. 69 × 10−19C) (1) 2 cm (2) 5 cm (3) 12 cm (4) 4 cm

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.An electron gun is placed inside a long solenoid of radius R on its axis. The solenoid has n turns/length and carries a current I. The electron gun shoots an electron along the radius of the solenoid with speed v. If the electron does not hit the surface of the solenoid, maximum possible value of v is (all symbols have their standard meaning): (1) eμ0nIR (2) eμ0nIR m 2m (3) eμ0nIR (4) 2eμ0nIR 4m m

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

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.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.A small bar magnet is placed with its axis at 30o with an external magnetic field of 0. 06 T experiences a torque of 0. 018 Nm. The minimum work required to rotate it from its stable to unstable equilibrium position is: (1) 6. 4 × 10−2 J (2) 9. 2 × 10−3 J (3) 7. 2 × 10−2 J (4) 11. 7 × 10−3 J

Q14.A charged particle (mass m and charge q) moves along X axis with velocity V0 . When it passes through the → origin it enters a region having uniform electric field E = −Eˆj which extends upto x = d. Equation of path of electron in the region x > d is: qEd qEd (1) y = (x −d) (2) y = ( d2 −x) mv2 mv2 0 0 qEd (3) y = (4) y = qEd2 x mv2 0 mv20

Q14.A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic → substance. The whole system is placed in a uniform magnetic field B . Then the field inside the paramagnetic substance is: → (1) (2) Zero B → → → → (3) (4) much large than B and parallel to B much large than B but opposite to B

Q14.A very long wire ABDMNDC is shown in figure carrying current I. AB and BC parts are straight, long and at right angle. At D wire forms a circular turn DMND of radius R. AB, BC parts are tangential to circular turn at JEE Main 2020 (08 Jan Shift 2) JEE Main Previous Year Paper N and D. Magnetic filed at the center of circle is: (1) + − 2πR μ0I (π 1 ) (2) 2πRμ0I (π 1 ) √2 √2 μ0I (3) 2πR (π + 1) (4) μ0I2R

Q14.A wire A , bent in the shape of an arc of a circle, carrying a current of 2 A and having radius 2 cm and another wire B, also bent in the shape of an arc of a circle, carrying a current of 3 A and having radius of 4 cm , are placed as shown in the figure. The ratio of the magnetic fields due to the wires A and B at the common centre O is: (1) 4 : 6 (2) 6 : 4 (3) 2 : 5 (4) 6 : 5

Q14.In LC circuit the inductance L = 40 mH and capacitance C = 100 μF. If a voltage V (t) = 10sin(314t) is applied to the circuit, the current in the circuit is given as: (1) 0.52 cos(314t) (2) 10 cos(314t) (3) 5.2 cos(314t) (4) 0.52 sin(314t)

Q14.A LCR circuit behaves like a clamped harmonic oscillator. Comparing it with a physical spring-mass damped oscillator having damping constant 'b', the correct equivalence would be: (1) L ↔m, C ↔k, R ↔b (2) L ↔1b , C ↔ m1 , R ↔1k (3) L ↔k, C ↔b, R ↔m (4) L ↔m, C ↔1k , R ↔b

Q14.A long, straight Wire of radius a carries a current distributed uniformly over its cross-section. The ratio of the magnetic fields due to the wire at distance a and 2a , respectively from the axis of the wire is: 3 (1) 2 (2) 2 3 (3) 1 (4) 3 2 2 −

Q14.In the circuit, given in the figure currents in different branches and value of one resistor are shown. Then potential at point B with respect to the point A is: (1) +2V (2) −2V (3) –1V (4) +1V