Current Electricity PYQs Set 23 (PDF)

Set 23 of 25 · Questions 661-690 of 723

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Mere Teacher · Previous Year Questions JEE Main Physics · Current Electricity · Set 23 (Q661-690)
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661. $The length of a potentiometer wire is 1200 cm and it carries a current of 60 mA . For a cell of emf 5 V and internal resistance of 20 Ω, the null point on it is found to be at 1000 cm . The resistance of whole wire is:$ (1) $80Ω$ (2) $100Ω$ (3) $120Ω$ (4) $60Ω$ 662. $A battery consists of a variable number n of identical cells (having internal resistance r each) which are connected in series. The terminals of the battery are short-circuited and the current I is measured. Which of the graphs shows the correct relationship between I and n ?$ (1) (2) (3) (4) 663. $Model a torch battery of length l to be made up of a thin cylindrical bar of radius 'a' and a concentric thin cylindrical shell of radius 'b' filled in between with an electrolyte of resistivity ρ (see figure). If the battery is connected to a resistance of value R, the maximum Joule heating in R will take place for$ (1) $R = \frac{ρ}{π l} ln (\frac{b}{a})$ (2) $R = \frac{2 ρ}{π l} ln (\frac{b}{a})$ (3) $R = \frac{ρ}{2 π l} ln (\frac{b}{a})$ (4) $R = \frac{ρ}{2 π} (\frac{b}{a})$ 664. $A circular wire has current density J = (2 \times 1 0^{10} \frac{A}{m ^{2}}) r^{2}, where r is the radial distance, out of the wire radius is 2 mm . The end-to-end potential applied to the wire is 50 V . How much energy (in joule) is converted to thermal energy in 100 s ?$ (1) $1200 π$ (2) $800 π$ (3) $3200 π$ (4) $600 π$ 665. $The current i in the network is:$ (1) $0.2 A$ (2) $0.3 A$ (3) $0 A$ (4) $0.6 A$ 666. $Which of the following resistivity (ρ) v / s temperature (T) curves is most suitable to be used in wire bound standard resistors?$ (1) (2) (3) (4) 667. $The current flowing through R_{2} is:$ (1) $\frac{2}{3} A$ (2) $\frac{1}{2} A$ (3) $\frac{1}{3} A$ (4) $\frac{1}{4} A$ 668. $The drift velocity of electrons for a conductor connected in an electrical circuit is V_{d} . The conductor in now replaced by another conductor with same material and same length but double the area of cross section. The applied voltage remains same. The new drift velocity of electrons will be$ (1) $V_{d}$ (2) $\frac{V _{d}}{2}$ (3) $\frac{V _{d}}{4}$ (4) $2 V_{d}$ 669. $For the circuit shown in the figure$ (1) $the current I through the battery is 7.5 mA$ (2) $the potential difference across R_{L} is 18 V$ (3) $ratio of powers dissipated in R_{1} and R_{2} is 3$ (4) $if R_{1} and R_{2} are interchanged, magnitude of the power dissipated in R_{L} will decrease by a factor of 9$ 670. $Given below are two statements: Statement I: A uniform wire of resistance 80 Ω is cut into four equal parts. These parts are now connected in parallel. The equivalent resistance of the combination will be 5 Ω . Statement II: Two resistance 2R and 3R are connected in parallel in a electric circuit. The value of thermal energy developed in 3R and 2R will be in the ratio 3:2. In the light of the above statements, choose the most appropriate answer from the options given below$ (1) $Both statement I and statement II are correct$ (2) $Both statement I and statement II are incorrect$ (3) $Statement I is correct but statement II is incorrect$ (4) $Statement I is incorrect but statement II is correct$ 671. $The current in the following circuit is$ (1) $2/3 A$ (2) $1 A$ (3) $1/8 A$ (4) $2/9 A .$ 672. $A 5‐ampere fuse wire can withstand a maximum power of 1 watt in the circuit. The resistance of the fuse wire is$ (1) $0.04 ohm$ (2) $0.2 ohm$ (3) $5 ohm$ (4) $0.4 ohm.$ 673. $The current in the given circuit is$ (1) $4.9 A$ (2) $6.8 A$ (3) $8.3 A$ (4) $2.0 A$ 674. $This question has Statement I and Statement II. Of the four choices given after the Statements, choose the one that best describes the two Statements Statement -I: For higher range, the resistance of ammeter (R_{A} \approx shunt resistance) should be more. Statement -II: To increase the range of ammeter, additional shunt needs to be used across it.$ (1) $Statement -II is true, Statement -II is true, Statement -II is the correct explanation of Statement -I.$ (2) $Statement -I is true, Statement - II is true, Statement -II is not the correct explanation of Statement -II.$ (3) $Statement -I is true, Statement - II is false$ (4) $Statement -I is false, Statement - II is true.$ 675. $A moving coil galvanometer has resistance 50 Ω and it indicates full deflection at 4 mA current. A voltmeter is made using this galvanometer and a 5 kΩ resistance. The maximum voltage, that can be measured using this voltmeter, will be close to:$ (1) $40 V$ (2) $15 V$ (3) $20 V$ (4) $10 V$ 676. $This question has Statement I and Statement II. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement -I: Higher the range, greater is the resistance of ammeter. Statement -II: To increase the range of ammeter, additional shunt needs to be used across it.$ (1) $Statement -I is true, Statement -II is true, Statement -II is the correct explanation of Statement -I.$ (2) $Statement -I is true, Statement - II is true, Statement -II is not the correct explanation of Statement -I$ (3) $Statement -I is true, Statement - II is false.$ (4) $Statement -I is false, Statement - II is true.$ 677. $An infinite line charge of uniform electric charge density λ lies along the axis of an electrically conducting infinite cylindrical shell of radius R. At time t = 0, the space inside the cylinder is filled with a material of permittivity ε and electrical conductivity σ. The electrical conduction in the material follows Ohm's law. Which one of the following graphs best describes the subsequent variation of the magnitude of current density j (t) at any point in the material?$ (1) (2) (3) (4) 678. $What will be the most suitable combination of three resistors A = 2 Ω, B = 4 Ω, C = 6 Ω so that (\frac{22}{3}) Ω is equivalent resistance of combination?$ (1) $Parallel combination of A and C connected in series with B.$ (2) $Parallel combination of A and B connected in series with C.$ (3) $Series combination of A and C connected in parallel with B.$ (4) $Series combination of B and C connected in parallel with A.$ 679. $A battery of emf 10 V and internal resistance 3 ohm is connected to a resistor. The current in the circuit is 0.5 A . The terminal voltage of the battery when the circuit is closed is$ (1) $10 V$ (2) $0 V$ (3) $1.5 V$ (4) $8.5 V$ 680. $A potentiometer circuit is set up as shown. The potential gradient, across the potentiometer wire, is kvolt / cm and the ammeter, present in the circuit, reads 1.0 A when two way key is switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1 and 3, is plugged in, are found to be at lengths l_{1} cm and l_{2} cm respectively The magnitudes, of the resistors R and X, in ohms, are then, equal, respectively, to$ (1) $k (l_{2} - l_{1}) and k l_{2}$ (2) $k l_{1} and k (l_{2} - l_{1})$ (3) $k (l_{2} - l_{1}) and k l_{1}$ (4) $k l_{1} and k l_{2}$ 681. $The reading of the ammeter (A) in steady state in the following circuit (assuming negligible internal resistance of the ammeter) is____A.$ (1) $1$ (2) $1/2$ (3) $0$ (4) $2$ 682. $The potential difference (V_{A} - V_{B}) between the points A and B in the given figure is$ (1) $- 3 V$ (2) $+ 3 V$ (3) $+ 6$ (4) $+ 9 V$ 683. $In the given circuit, the potential at the point B with respect to the point A is$ (1) $6 V$ (2) $- 6 V$ (3) $2 V$ (4) $- 2 V$ 684. $The effective resistance between A and B, if resistance of each resistor is R, will be$ (1) $\frac{8 R}{3}$ (2) $\frac{5 R}{3}$ (3) $\frac{4 R}{3}$ (4) $\frac{2}{3} R$ 685. $An electric bulb of 500 watt at 100 volt is used in a circuit having a 200V supply. Calculate the resistance R to be connected in series with the bulb so that the power delivered by the bulb is 500W.$ (1) $20Ω$ (2) $30Ω$ (3) $5Ω$ (4) $10Ω$ 686. $A resistor dissipates 192J of energy in 1s when a current of 4A is passed through it. Now, when the current is doubled, the amount of thermal energy dissipated in 5s in..... J.$ 687. $Two cells of emfs 1 V and 2 V and internal resistances 2Ω and 1Ω, respectively, are connected in series with an external resistance of 6Ω . The total current in the circuit is I_{1} . Now the same two cells in parallel configuration are connected to same external resistance. In this case, the total current drawn is I_{2} . The value of (\frac{I _{1}}{I _{2}}) is \frac{x}{3} . The value of x is _____.$ 688. $The current I flowing through the given circuit will$ 689. $In the figure given, the electric current flowing through the 5 kΩ resistor is ’ x^{’} mA . The value of x to the nearest integer is\dots\dots$ 690. $Two resistors are connected in series across a battery as shown in figure. If a voltmeter of resistance 2000 Ω is used to measure the potential difference across 500 Ω resister, the reading of the voltmeter will be____V.$