Current Electricity PYQs Set 22 (PDF)

Set 22 of 25 · Questions 631-660 of 723

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Mere Teacher · Previous Year Questions JEE Main Physics · Current Electricity · Set 22 (Q631-660)
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631. $A current of 6 A enters one corner P of an equilateral triangle PQR having 3 wires of resistances 2Ω each and leaves by the corner R . Then the current I_{1} and I_{2} are$ (1) $2 A, 4 A$ (2) $4 A, 2 A$ (3) $1 A, 2 A$ (4) $2 A, 3 A$ 632. $The range of an ammeter of resistance ' G' can be increased from I to nI by connecting$ (1) $a series resistance of \frac{G}{n - 1} Ω$ (2) $a shunt of \frac{G}{n - 1} Ω$ (3) $a shunt of \frac{G}{n + 1} Ω .$ (4) $a series resistance of \frac{G}{n + 1} Ω .$ 633. $When a wire of uniform cross‐section a, length l and resistance R is bent into a complete circle, resistance between any two of diametrically opposite points will be$ (1) $R /4$ (2) $4 R$ (3) $R /8$ (4) $R /2$ 634. $A cell of internal resistance r drives current through an external resistance R. The power delivered by the cell to the external resistance will be maximum when:$ (1) $R = 0.001 r$ (2) $R = 1000 r$ (3) $R = 2 r$ (4) $R = r$ 635. $A circuit contains an ammeter, a battery of 30 V and a resistance 40.8Ω all connected in series. If the ammeter has a coil of resistance 480Ω and a shunt of 20Ω, then reading in the ammeter will be$ (1) $0.5 A$ (2) $0.25 A$ (3) $2 A$ (4) $1 A$ 636. $Five current carrying conductors meet at a point P. What is the magnitude and direction of the current in the fifth conductor?$ (1) $1 A from Q to P$ (2) $1 A from P to Q$ (3) $3 A from P to Q$ (4) $2 A from Q to P$ 637. $Two ideal batteries of emf V_{1} and V_{2} and three resistances R_{1}, R_{2} and R_{3} are connected as shown in the figure. The current in resistance R_{2} would be zero if$ (1) $V_{1} = V_{2} and R_{1} = R_{2} = R_{3}$ (2) $V_{1} = V_{2} and R_{1} = 2 R_{2} = R_{3}$ (3) $V_{1} = 2 V_{2} and 2 R_{1} = 2 R_{2} = R_{3}$ (4) $2 V_{1} = V_{2} and 2 R_{1} = R_{2} = R_{3}$ 638. $A Copper (Cu) rod of length 25cm and cross-sectional area 3 m m^{2} is joined with a similar Aluminium (Al) rod as shown in figure. Find the resistance of the combination between the ends A and B. (Take Resistivity of Copper = 1.7 \times 1 0^{- 8} ΩM Resistivity of Aluminium = 2.6 \times 1 0^{- 8} Ωm)$ (1) $2.170 m Ω$ (2) $1.420 m Ω$ (3) $0.0858 m Ω$ (4) $0.858 m Ω$ 639. $In the given figure, the emf of the cell is 2.2V and if internal resistance is 0.6Ω . Calculate the power dissipated in the whole circuit:$ (1) $1.32W$ (2) $0.65W$ (3) $2.2W$ (4) $4.4W$ 640. $The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10Ω is:$ (1) $0.5$ (2) $0.8$ (3) $1.0$ (4) $0.2$ 641. $Find the mobility of electron in a wire, if its average collision time is 9.1 \times 1 0^{- 15} s . (charge of electron = 1.6 \times 1 0^{- 19} C and mass of electron (= 9.1 \times 1 0^{- 31} kg)$ (1) $9.1\times 1 0^{- 3} m2/V-s$ (2) $1.6 \times 10^{- 3} m^{2} / V - s$ (3) $1.75 \times 10^{- 3} m^{2} / V - s$ (4) $1 \times 10^{- 3} m^{2} / V - s$ 642. $Find the resistance of a cube of edge 60 cm, made of a material of specific resistance 60 \times 10^{- 8} Ωm .$ (1) $2.5 \times 1 0^{- 5} Ω$ (2) $1 0^{- 8} Ω$ (3) $1 0^{- 6} Ω$ (4) $5 \times 1 0^{- 4} Ω$ 643. $A current of 2 A, passing through a conductor produces 80 J of heat in 10 seconds. The resistance of the conductor in ohm is$ (1) $0.5$ (2) $2$ (3) $4$ (4) $20$ 644. $In a meter bridge experiment null point is obtained at l cm from the left end. If the meter bridge wire is replaced by a wire of same material but twice the area of cross-section, then the null point is obtained at a distance$ (1) $2 l cm from left end$ (2) $l cm from left end$ (3) $\frac{l}{2} cm from left end$ (4) $\frac{l}{4} cm from left end$ 645. $A uniform metallic wire carries a current 2 A. when 3.4 V battery is connected across it. The mass of uniform metallic wire is 8.92 \times 1 0^{- 3} kg. density is 8.92 \times 1 0^{3} kg/ m^{3} and resistivity is 1.7 \times 1 0^{- 8} Ω -m. The length of wire is:$ (1) $l =6.8m$ (2) $l =10m$ (3) $l = 5m$ (4) $l =100m$ 646. $A cell can be balanced against 100 cm and 110 cm of potentiometer wire, respectively with and without being short circuited through a resistance of 10 Ω . Its internal resistance is$ (1) $2.0 ohm$ (2) $zero$ (3) $1.0 ohm$ (4) $0.5 ohm$ 647. $The quantities that don't change when a resistor connected to a battery is heated due to the current are (A) drift speed (B) resistivity (C) Resistance (D) Number of free electrons$ (1) $B and C$ (2) $D$ (3) $A$ (4) $A and D$ 648. $(A) The drift velocity of electrons decreases with the increase in the temperature of conductor. (B) The drift velocity is inversely proportional to the area of cross-section of given conductor. (C) The drift velocity does not depend on the applied potential difference to the conductor. (D) The drift velocity of electron is inversely proportional to the length of the conductor. (E) The drift velocity increases with the increase in the temperature of conductor. Choose the correct answer from the options given below:$ (1) $A and B only$ (2) $A and D only$ (3) $B and E only$ (4) $B and C only$ 649. $Wire bound resistors are made by$ (1) $winding the wires of an alloy of Ge, Au, Ga$ (2) $winding the wires of an alloy of Cu, Al, Ag$ (3) $winding the wires of an alloy of manganic, constantan, nichrome$ (4) $winding the wires of an alloy of Si, Tu, Fe$ 650. $A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance R, connected across the given cell, has values of (i) infinity (ii) 9.5 Ω the balancing lengths on the potentiometer wire are found to be 3 m and 2.85 m, respectively The value of internal resistance of the cell is$ (1) $0.25 Ω$ (2) $0.95 Ω$ (3) $0.5 Ω$ (4) $0.75 Ω$ 651. $One kilowatt hour is equal to$ (1) $36 \times 1 0^{- 5} J$ (2) $36 \times 1 0^{- 4} J$ (3) $36 \times 1 0^{5} J$ (4) $36 \times 1 0^{3} J$ 652. $Consider an electrical conductor connected across a potential difference V. Let Δ q be a small charge moving through it in time Δ t . If I is the electric current through it, (i) the kinetic energy of the charge increases by IV Δ t . (ii) the electric potential energy of the charge decreases by IV Δ t . (iii) the thermal energy of the conductor increases by IV Δ t . Then the correct statement/s is/are$ (1) $(i)$ (2) $(i) and (ii)$ (3) $(i) and (iii)$ (4) $(ii) and (iii)$ 653. $A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of. (i) infinity (ii) 9.5Ω The 'balancing lengths, on the potentiometer wire are found to be 3m and 2.85 m, respectively. The value of internal resistance of the cell is:$ (1) $0.25$ (2) $0.95$ (3) $0.5$ (4) $0.75$ 654. $Ohm's law is applicable to$ (1) $diode$ (2) $transistor$ (3) $electrolyte$ (4) $conductor$ 655. $Statement (I): Specific resistance depends on nature of material and independent of temperature of the material. Statement (II): A wire of resistance 6Ω is drawn out so that its new length is four times its original length. The resistance of the new wire is 48Ω . Statement (III): Drift velocity is the average constant velocity acquired by free electrons inside a metal by the application of an electric field which results in current. Which of the following is correct?$ (1) $Statements I, II and III are true$ (2) $Statement I is true, but statements II, III is false$ (3) $Statement III is true, but statements I, II are false$ (4) $Statements II, III are true, but statement I is false$ 656. $A potentiometer wire of length L and a resistance r are connected in series with a battery of e.m.f. E_{0} and a resistance r_{1} . An unknown e.m.f. E is balanced at a length l of the potentiometer wire. The e.m.f. E will be given by$ (1) $\frac{E _{0} l}{L}$ (2) $\frac{L E _{0} r}{( r + r _{1} ) l}$ (3) $\frac{L E _{0} r}{l r _{1}}$ (4) $\frac{E _{0} r}{( r + r _{1} )} \frac{l}{L}$ 657. $Two identical cells, when connected either in parallel or in series gives same current in an external resistance 5 Ω . The internal resistance of each cell will be________Ω .$ 658. $In a meter bridge experiment to determine the value of unknown resistance, first the resistances 2Ω and 3Ω are connected in the left and right gaps of the bridge and the null point is obtained at a distance l cm from the left. Now when an unknown resistance xΩ is connected in parallel to 3Ω resistance, the null point is shifted by 10 cm to the right of wire. The value of unknown resistance x is____Ω .$ 659. $Seawater at a frequency f = 9 \times 10^{2} Hz, haspermittivity ϵ = 80 ϵ_{0} and resistivity ρ = 0.25 Ωm . Imagine a parallel plate capacitor is immersed in seawater and is driven by an alternating voltage source V (t) = V_{0} sin (2 πft) . Then theconduction current density becomes 10^{x} times the displacement current density after time t = \frac{1}{800} s . The value of x is____ (Given: (\frac{1}{4 π ϵ _{0}} = 9 \times 10^{9} Nm^{2} C^{- 2})$ 660. $A moving coil galvanometer has 50 turns and each turn has an area 2 \times 1 0^{-4} m^{2} . The magnetic field produced by the magnet inside the galvanometer is 0.02T. The torsional constant of the suspension wire is 1 0^{-4} Nm r a d^{-1} . When a current flows through the galvanometer, a full scale deflection occurs if the coil rotates by 0.2 rad. The resistance of the coil of the galvanometer is 50Ω. This galvanometer is to be converted into an ammeter capable of measuring current in the range 0 - 1.0A. For this purpose, a shunt resistance is to be added in parallel to the galvanometer. The value of this shunt resistance, in ohms, is __________.$