Practice Questions

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

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 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.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.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

Q18.A wire of resistance R is bent to form a square ABCD as shown in the figure. The effective resistance between E and C is: ( E is mid-point of arm CD ) (1) R (2) 7 R 64 (3) 1 R (4) 3 R 16 4 JEE Main 2019 (09 Apr Shift 1) JEE Main Previous Year Paper

Q18.A galvanometer having a resistance of 20Ω and 30 division on both sides has figure of merit 0.005 ampere/ division. The resistance that should be connected in series such that it can be used as a voltmeter upto 15 volt, is: (1) 100Ω (2) 120Ω (3) 80Ω (4) 125Ω

Q18.A simple pendulum of length L is placed between the plates of a parallel plate capacitor having electric field E , as shown in figure. Its bob has mass m and charge q . The time period of the pendulum is given by: L L (1) 2π (2) 2π qE qE 2 √ g + m √ √g2 + m (3) 2π LqE (4) 2π L 2 √ g - m √ √g2 - q2Em2

Q18.Two electric bulbs, rated at (25 W, 220 V) and (100 W, 220 V), are connected in series across a 220 V voltage source. If the 25 W and 100 W bulbs draw powers P1 and P2 respectively, then: (1) P1 = 4 W, P2 = 16 W (2) P1 = 9 W, P2 = 16 W (3) P1 = 16 W, P2 = 9 W (4) P1 = 16 W, P2 = 4 W

Q18.A galvanometer of resistance 100 Ω has 50 divisions on its scale and has sensitivity of 20μA / division . It is to be converted to voltmeter with three ranges, of 0 - 2 V, 0 - 10 V and 0 - 20 V . The appropriate circuit to do so is: JEE Main 2019 (12 Apr Shift 1) JEE Main Previous Year Paper (1) (2) (3) (4)

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

Q18.In the circuit shown, a four-wire potentiometer is made of a 400 cm long wire, which extends between A and B . The resistance per unit length of the potentiometer wire is r = 0.01 Ω / cm . If an ideal voltmeter is JEE Main 2019 (08 Apr Shift 2) JEE Main Previous Year Paper connected as shown with jockey J at 50 cm from end A , the expected reading of the voltmeter will be: (1) 0.50 V (2) 0.25 V (3) 0.75 V (4) 0.20 V

Q18.A parallel plate capacitor having capacitance 12 pF is charged by a battery to a potential difference of 10 V between its plates. The charging battery is now disconnected and a porcelain slab of dielectric constant 6.5 is slipped between the plates. The work done by the capacitor on the slab is (1) 560 pJ (2) 600 pJ (3) 508 pJ (4) 692 pJ

Q18.In the given circuit the internal resistance of the 18V cell is negligible. If R1 = 400 Ω, R3 = 100 Ω and R4 = 500 Ω and the reading of an ideal voltmeter across R4 is 5 V , then the value of R2 will be: JEE Main 2019 (09 Jan Shift 2) JEE Main Previous Year Paper (1) 550 Ω (2) 300 Ω (3) 450 Ω (4) 230 Ω

Q18.Drift speed of electrons, when 1.5 A current flows in a copper wire of cross section 5 mm2 is 𝑣𝑑. If the electron density in copper is 9 × 1028 m-3 the value of 𝑣𝑑 in mm 𝑠-1 is close to (Take charge of an electron to be = 1.6 × 10-19 C) (1) 0.2 (2) 3 (3) 2 (4) 0.02

Q18.A moving coil galvanometer, having a resistance G, produces full scale deflection when a current IG flows through it. This galvanometer can be converted into (i) an ammeter of range 0 to Io(I0 > Ig) by connecting a shunt resistance RA to it and (ii) into a voltmeter of range 0 to V(V = GI0) by connecting a series resistance RV to it. Then, JEE Main 2019 (12 Apr Shift 2) JEE Main Previous Year Paper Ig (1) = and RA = 2 (2) RARV = G2 and RARV RARV = (I0−Ig) RV G2( I0−IgIg ) ( (I0−Ig)Ig ) (3) Ig RA I0−Ig 2 (4) RA Ig 2 RARV = G2( I0−Ig ) and RV = ( Ig ) RARV = G2 and RV = ( I0−Ig )

Q19.The actual value of resistance R , shown in the figure is 30Ω. This is measured in an experiment as shown using the standard formula R = VI , where V and I are the readings of the voltmeter and ammeter, respectively. If the measured value of R is 5% less, then the internal resistance of the voltmeter is: (1) 35Ω (2) 600Ω (3) 570Ω (4) 350Ω

Q19.A paramagnetic substance in the form of a cube with sides 1 cm has a magnetic dipole moment of 20 × 10−6 J/T when a magnetic intensity of 60 × 103 A/m is applied. Its magnetic susceptibility is: JEE Main 2019 (11 Jan Shift 2) JEE Main Previous Year Paper (1) 3.3 × 10−2 (2) 4.3 × 10−2 (3) 2.3 × 10−2 (4) 3.3 × 10−4 →

Q19.A particle having the same charge as of electron moves in a circular path of radius 0.5 cm under the influence of a magnetic field of 0.5 T. If an electric field of 100 V/m makes it to move in a straight path, then the mass of the particle is (Given charge of electron = 1.6 × 10−19C ) (1) 9.1 × 10−31 kg (2) 1.6 × 10−27 kg (3) 2.0 × 10−24 kg (4) 1.6 × 10−19 kg

Q19.A paramagnetic material has 1028 atoms m−3 . Its magnetic susceptibility at temperature 350 K is 2.8×10−4 . Its susceptibility at 300 K is (1) 3.726 x 10−4 (2) 2.672 x 10−4 (3) 3.267 x 10−4 (4) 3.672 x 10−4 JEE Main 2019 (12 Jan Shift 2) JEE Main Previous Year Paper