Practice Questions

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 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.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 )

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.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 200 Ω resistor has certain colour code. If one replaced the red colour by green in the code, the new resistance will be: (1) 300 Ω (2) 100 Ω (3) 400 Ω (4) 500 Ω

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 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.The resistance of a galvanometer is 50 ohm and the maximum current which can be passed through it is 0.002 A. What resistance must be connected to it in order to convert it into an ammeter of range 0 −0.5 A? (1) 0.2 ohm (2) 0.5 ohm (3) 0.002 ohm (4) 0.02 ohm

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 uniform metallic wire has a resistance of 18 Ω and is bent into an equilateral triangle. Then, the resistance between any two vertices of the triangle is: (1) 2 Ω (2) 12 Ω (3) 8 Ω (4) 4 Ω

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.In the given circuit diagram, the currents, I1 = −0.3 A, I4 = 0.8 A and I5 = 0.4 A, are flowing as shown. The currents I2, I3 and I6, respectively, are: (1) 0.4A, 1.1A, 0.4A (2) 1.1A, −0.4A, 0.4A (3) 1.1A, 0.4A, 0.4A (4) −0. 4A, 0. 4A, 1. 1A

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.In an experiment, the resistance of a material is plotted as a function of temperature (in some range). As shown in the figure, it is a straight line. One may conclude that 0 (2) R(T) = R0 (1) R(T) = R0eT2/T2 T2 (3) R(T) = R0e−T2/T2 0 (4) R(T) = R0e−T20/T2

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 2 W carbon resistor is color coded with green, black, red and silver respectively. The maximum current which can be passed through this resistor is: (1) 100 mA (2) 0.4 mA (3) 20 mA (4) 63 mA

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

Q19.In an experiment, electrons are accelerated, from rest, by applying a voltage of 500 V . Calculate the radius of the path if a magnetic field 100mT is then applied. [Charge of the electron = 1.6 × 10−19C Mass of the electron = 9.1 × 10−31 kg] (1) 7.5 × 10−3 m (2) 7.5 × 10−2 m (3) 7.5 m (4) 7.5 × 10−4 m

Q19.The resistive network shown below is connected to a D . C . source of 16 V . The power consumed by the network is 4 Watt. The value of R is: (1) 16 Ω (2) 8 Ω (3) 6 Ω (4) 1 Ω

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 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 circular coil having N turns and radius r carries a current I . It is held in the XZ plane in a magnetic field B^i . The torque on the coil due to the magnetic field is: (1) Bπr2IN (2) Br2I (3) Bπr2I (4) Zero πN N

Q19.An electron, moving along the x− axis with an initial energy of 100 eV, enters a region of magnetic field → B = (1.5 × 10−3 T)ˆk at S (see figure). The field extends between x = 0 and x = 2 cm. The electron is detected at the point Q on a screen placed 8 cm away from the point S. The distance d between P and Q (on the screen) is: (electron’s charge 1.6 × 10−19 C , mass of electron = 9.1 × 10−31 kg ) (1) 1.22 cm (2) 12.87 cm (3) 11.65 cm (4) 2.25 cm

Q19.Mobility of electrons in a semiconductor is defined as the ratio of their drift velocity to the applied electric field. If, for an N-type semiconductor, the density of electrons is 1019 m-3 and their mobility is 1.6 m2 V-1 s-1, then the resistivity of the semiconductor (since it is an N-type semiconductor contribution of holes is ignored) is close to: (1) 0.2 Ω m (2) 4 Ω m (3) 2 Ω m (4) 0.4 Ω m