Practice Questions

Q16.In the given circuit, an ideal voltmeter connected across the 10 Ω resistance reads 2 V . The internal resistance r , of each cell is: (1) 0 Ω (2) 1.5 Ω (3) 0.5 Ω (4) 1 Ω

Q16.A parallel plate capacitor is made of two square plates of side 𝑎, separated by a distance 𝑑 𝑑≪𝑎. The lower triangular portion filled with a dielectric of dielectric constant 𝐾, as shown in the figure. Capacitance of this JEE Main 2019 (09 Jan Shift 1) JEE Main Previous Year Paper capacitor is: (1) 𝐾𝜀0𝑎2 (2) 𝐾𝜀0𝑎2 2𝑑𝐾+ 1 𝑑𝐾- 1ln⁡𝐾 (3) 𝐾𝜀0𝑎2 ln⁡𝐾 (4) 1 𝐾𝜀0𝑎2 𝑑 2 𝑑

Q16.A parallel plate capacitor is of area 6 cm2 and a separation 3 mm. The gap is filled with three dielectric materials of equal thickness (see figure) with dielectric constant K1 = 10, K2 = 12 and K3 = 14. The dielectric constant of a material which when fully inserted in above capacitor, gives same capacitance would be: (1) 4 (2) 36 (3) 14 (4) 12

Q16.In the figure shown below, the charge on the left plate of the 10F capacitor is -30C. The charge on the right plate of the 6F capacitor is: (1) −12μC (2) +12μC (3) −18μC (4) +18μC

Q16.A source of sound S is moving with a velocity of 50 m s-1 towards a stationary observer. The observer measures the frequency of the source as 1000 Hz . What will be the apparent frequency of the source when it is moving away from the observer after crossing him? (Take velocity of sound in air is 350 m s-1 ) (1) 750 Hz (2) 857 Hz (3) 1143 Hz (4) 807 Hz

Q16.Seven capacitors, each of capacitance 2μF, are to be connected in a configuration to obtain an effective capacitance of ( 136 )μF. Which of the combinations, shown in figures below, will achieve the desired value? (1) (2) (3) (4)

Q16.The electric field in a region is given by →E = Ax + B ^i , where E is in NC-1 and 𝑥 is in metres. The values of constants are A = 20 SI unit and B = 10 SI unit. If the potential at 𝑥= 1 is V1 and that at 𝑥= - 5 is V2, then V1 - V2 is (1) 320 V (2) -520 V (3) 180 V (4) -48 V

Q16.Charges −q and +q , located at A and B, respectively, constitute an electric dipole. Distance AB = 2a, O is the mid point of the dipole and OP is perpendicular to AB. A charge Q is placed at P where OP = y and y ≫2a. The charge Q experiences an electrostatic force F . If Q is now moved along the equatorial line to P′ such that OP′= ( 3y ) the force on Q will be close to ( 3y ≪2a) (1) 27F . (2) F3 . (3) 3F . (4) 9F . JEE Main 2019 (10 Jan Shift 2) JEE Main Previous Year Paper

Q16.The parallel combination of two air filled parallel plate capacitors of capacitance C and nC is connected to a battery of voltage, V . When the capacitors are fully charged, the battery is removed and after that a dielectric material of dielectric constant K is placed the two plates of the first capacitor. The new potential difference of the combined system is: (1) (n+1)V (2) nV (K+n) K+n (3) V (4) V K+n

Q16.Let a total charge 2Q be distributed in a sphere of radius R, with the charge density given by ρ(r) = kr, where r is the distance from the centre. Two charges A and B , of −Q each, are placed on diametrically opposite points, at equal distance, a, from the centre. If A and B do not experience any force, then: (1) a = 3R1 (2) a = R 2 4 √3 (3) a = 2 −14 R (4) a = 8 −14 R

Q17.Four equal point charges Q each are placed in the xy plane at (0, 2), (4, 2), (4, −2) and (0, −2) . The work required to put a fifth charge Q at the origin of the coordinate system will be: (1) Q2 (2) Q2 4πϵ0 2√2πϵ0 (3) Q2 + 1 (4) Q2 + 1 4πϵ0 (1 √5 ) 4πϵ0 (1 √3 )

Q17.A metal wire of resistance 3 Ω is elongated to make a uniform wire of double its previous length. This new wire is now bent and the ends joined to make a circle. If two points on this circle make an angle 60o at the center, the equivalent resistance between these two points will be: (1) 5 3 Ω (2) 125 Ω (3) 7 2 Ω (4) 52 Ω

Q17.When the switch 𝑆, in the circuit shown, is closed, then the value of current 𝑖 will be: (1) 2 A (2) 5 A (3) 3 A (4) 4 A

Q17.Two equal resistances when connected in series to a battery, consume electric power of 60 W. If these resistance are now connected in parallel combination to the same battery, the electric power consumed will be : (1) 60 W (2) 240 W (3) 120 W (4) 30 W

Q17.In the given circuit, the charge on 4 μF capacitor will be: (1) 9.6 μC (2) 5.4 μC (3) 24 μC (4) 13.4 μC

Q17.For the circuit shown, with 𝑅1 = 1.0 Ω , 𝑅2 = 2.0 Ω , 𝐸1 = 2 V and 𝐸2 = 𝐸3 = 4 V, the potential difference between the points ‘a’ and ‘b’ is approximately ( in V ): (1) 3.3 (2) 2.3 (3) 2.7 (4) 3.7

Q17.An ideal battery of emf 4V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and resistance 5 Ω. The value of R, to give a potential difference of 5 mV across 10 cm of potentiometer wire, is: (1) 480 Ω (2) 495 Ω (3) 395 Ω (4) 490 Ω

Q17.In the given circuit the cells have zero internal resistance. The currents (in amperes) passing through resistance R1 and R2 respectively, are: (1) 0, 1 (2) 2, 2 (3) 0.5 , 0 (4) 1, 2

Q17.A galvanometer, whose resistance is 50 ohm, has 25 divisions in it. When a current of 4 × 10−4 A passes through it, its needle (pointer) deflects by one division. To use this galvanometer as a voltmeter of range 2.5 V it should be connected to a resistance of: (1) 6250 ohm (2) 250 ohm (3) 6200 ohm (4) 200 ohm

Q17.A capacitor with capacitance 5 μF is charged to 5 μC . If the plates are pulled apart to reduce the capacitance to 2 μF, how much work is done? (1) 6.25 × 10–6 J (2) 2.55 × 10–6 J (3) 2.16 × 10–6 J (4) 3.75 × 10–6 J

Q17.A carbon resistance has a following colour code. What is the value of the resistance? (1) 6.4 MΩ ± 5% (2) 64 kΩ ± 10% (3) 530 kΩ ± 5% (4) 5.3 MΩ ± 5%

Q17.A moving coil galvanometer allows a full scale current of 10−4 A . A series resistance of 2 × 104 Ω is required to convert the galvanometer into a voltmeter of range 0 −5 V . Therefore, the value of shunt resistance required to convert the above galvanometer into an ammeter of range 0 −10 mA is: JEE Main 2019 (10 Apr Shift 1) JEE Main Previous Year Paper (1) 100 Ω (2) 200 Ω (3) 300 Ω (4) 10 Ω

Q17.A parallel plate capacitor has 1μF capacitance. One of its two plates is given +2μC charge and the other plate, +4 μC charge. The potential difference developed across the capacitor is: (1) 1 V (2) 2 V (3) 3 V (4) 5 V

Q17. In the circuit shown, the potential difference between A and B is (1) 1 V (2) 2 V (3) 3V (4) 6 V

Q18.In a Wheatstone bridge (see fig.), Resistances P and Q are approximatelyequal. When R = 400Ω , the bridge is balanced. On interchanging P and Q, the value of R, for balance, is 405Ω . The value of Y is close to JEE Main 2019 (11 Jan Shift 1) JEE Main Previous Year Paper (1) 401.5ohm (2) 404.5ohm (3) 403.5ohm (4) 402.5ohm