Tiêu đề 3.CURRENT ELECTRICITY - Questions.pdf ✅

3.CURRENT ELECTRICITY 1(1.)There are three resistance coils of equal resistance. The maximum number of resistances you can obtain by connecting them in any manner you choose, being free to use any number of the coils in any way is (a.) 3 (b.) 4 (c.) 6 (d.) 5 2(2.)A wire when connected to 220V mains supply has power dissipation P1. Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is P2. Then P2 ∶ P1 is (a.) 1 (b.) 4 (c.) 2 (d.) 3 3(3.)In the circuit shown below, the power developed in the 6Ω resistor is 6 watt. The power in watts developed in the 4Ω resistor is (a.) 16 (b.) 9 (c.) 6 (d.) 4 4(4.)A 5°C rise in temperature is observed in a conductor by passing a current. When the current is doubled the rise in temperature will be approximately (a.) 16°C (b.) 10°C (c.) 20°C (d.) 12°C 5(5.)In Cu − Fe couple, the flow of current at the temperature of inversion is (a.) From Fe to Cu through the hot junction (b.) From Cu to Fe through the hot junction (c.) Maximum (d.) None of the above 6(6.)The resistance of an ideal voltmeter is (a.) Zero (b.) Very low (c.) Very large (d.) Infinite 7(7.)An electric wire of length ′L′ and area of cross- section a has resistance R ohm. Another wire of the same material having same length and area of cross-section 4a has a resistance of (a.) 4R (b.) R/4 (c.) R/16 (d.) 16R 8(8.)The potential difference in open circuit for a cell is 2.2 volt. When a 4 ohm resistor is connected between its two electrodes the potential difference becomes 2 volt. The internal resistance of the cell will be (a.) 1 ohm (b.) 0.2 ohm (c.) 2.5 ohm (d.) 0.4 ohm 9(9.)The mass of a substance liberated when a charge ′q′ flows through an electrolyte is proportional to (a.) q (b.) 1/q (c.) q 2 (d.) 1/q 2 10(10.)Two resistance of 10 Ω and 20 Ω and an inductor of inductance 5 H are connected to a battery of 2 V through a key k as shown in the figure. At time t = 0, when the key k is closed the initial current through the battery is (a.) 0.2 A (b.) 2 15 A (c.) 1 15 A (d.) 0 11(11.)What is the equivalent resistance across the points A and B in the circuit given below?
(a.) 8 Ω (b.) 12 Ω (c.) 16 Ω (d.) 32 Ω 12(12.)A hot electric iron has a resistance of 80 Ω and is used on a 200 V source. The electrical energy spent, if it is used for two hours, will be (a.) 8000 Wh (b.) 2000 Wh (c.) 1000 Wh (d.) 800 Wh 13(13.)In the process of electrolysis, the current is carried out inside the electrolyte by (a.) Electrons (b.) Atoms (c.) Positive and negative ions (d.) All the above 14(14.)For a given temperature difference which of the following pairs will generate maximum thermo- emf? (a.) Lead-nickel (b.) Copper-iron (c.) Gold-silver (d.) Antimony-bismuth 15(15.)Two resistors of resistances 200 kΩ and 1MΩ respectively form a potential divider with outer junctions maintained at potentials of +3V and −15V. Then, the potential at the junction between the resistors is (a.) +1 V (b.) −0.6 V (c.) 0 V (d.) −12 V 16(16.)A resistance of 2Ω is to be made from a copper wire (specific resistance=1.7 × 10−8Ω m) using a wire of length 50cm. The radius of the wire is (a.) 0.0116 mm (b.) 0.367 mm (c.) 0.116 mm (d.) 0.267 mm 17(17.)Five conductors are meeting at a point x as shown in the figure. What is the value of current in fifth conductor? (a.) 3 A away from x (b.) 1 A away from x (c.) 4 A away from x (d.) 1 A towards x 18(18.)In a closed circuit, the current I(in ampere) at an instant of time t(in second) is given by I = 4 − 0.08t. The number of electrons flowing in 50s through the cross-section of the conductor is (a.) 1.25 × 1019 (b.) 6.25 × 1020 (c.) 5.25 × 1019 (d.) 2.55 × 1020 19(19.)If voltage across a bulb rated 220 Volt-100 Watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is (a.) 20% (b.) 2.5% (c.) 5% (d.) 10% 20(20.)In the following circuit a 10 m long potentiometer wire with resistance 1.2 ohm/m, a resistance R1 and an accumulator of emf 2 V are connected in series. When the emf of thermocouple is 2.4 mV then the deflection in galvanometer is zero. The current supplied by the accumulator will be (a.) 4 × 10−4A (b.) 8 × 10−4A (c.) 4 × 10−3A (d.) 8 × 10−3A 21(21.)In a Wheatstone’s network P = 2Ω, Q = 2Ω, R = 2Ω and S = 3Ω. The resistance with which S is to be shunted in order that the bridge may be balanced is (a.) 1 Ω (b.) 2 Ω
10Ω (c.) 4 Ω (d.) 6 Ω 22(22.)An electron (charge = 1.6 × 10−19coulomb) is moving in a circle of radius 5.1 × 10−11m at a frequency of 6.8 × 1015 revolutions/sec. The equivalent current is approximately (a.) 5.1 × 10−3amp (b.) 6.8 × 10−3amp (c.) 1.1 × 10−3amp (d.) 2.2 × 10−3amp 23(23.)A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be (a.) Doubled (b.) Four times (c.) One-fourth (d.) Halved 24(24.)If two wires having resistances R and 2R both are joined in series and in parallel, then ratio of heat generated in this situation, applying the same voltage is (a.) 2 :1 (b.) 1 :2 (c.) 2 :9 (d.) 9 :2 25(25.)A 6V cell with 0.5 Ω internal resistance, a10V cell with 1 Ω internal resistance and a 12 Ω external resistance are connected in parallel. The current (in ampere) through the 10V cell is (a.) 0.60 (b.) 2.27 (c.) 2.87 (d.) 5.14 26(26.)A heater of 220 V heats a volume of water in 5 min. The same heater when connected to 110 V heats the same volume of water in (minute) (a.) 5 (b.) 20 (c.) 10 (d.) 2.5 27(27.)The deflection in a moving coil galvanometer is reduced to half when it is shunted with a 40 Ω coil. The resistance of the galvanometer is (a.) 15 Ω (b.) 20 Ω (c.) 40 Ω (d.) 80 Ω 28(28.)In a region 1019 α −particales and 1019 protons move to the left, while 1019 electrons move to the right per second. The current is (a.) 3.2 A towards left (b.) 3.2 A towards right (c.) 6.4 A towards left (d.) 6.4 A towards right 29(29.)The reading of a high resistance voltmeter when a cell is connected across it is 2.2 V. When the terminals of the cell are also connected to a resistance of 5 Ω the voltmeter reading drops to 1.8 V. Find the internal resistance of the cell (a.) 1.2 Ω (b.) 1.3 Ω (c.) 1.1 Ω (d.) 1.4 Ω 30(30.)When an electric heater is switched on, the current flowing through it (i) is plotted against time (t). Taking into account the variation of resistance with temperature, which of the following best represents the resulting curve (a.) (b.) (c.) (d.) 31(31.)The current in the given circuit is (a.) 0.3A (b.) 0.4A (c.) 0.1A (d.) 0.2A 32(32.)Every atom makes one free electron in copper. If 1.1 A Current is flowing in the wire of copper having 1 mm diameter, then the drift velocity(approx.) will be (density of copper=9 × 103 kg m−3 and atomic weight of copper=63) (a.) 0.1 mms −1 (b.) 0.2 mms −1 (c.) 0.3 mms −1 t I t I t I t I 2 V A B 20 Ω 5 V
(d.) 0.2 mms −1 33(33.)A current of 1.5 A flows through a copper voltmeter. The thickness of copper deposited on the electrode surface of area 50 cm2 in 20 min is (density of Cu=9000 kgm−3 ; ECE of Cu = 3.3 × 10−7kgC −1 ) (a.) 1.3 × 10−4 m (b.) 1.3 × 10−5 m (c.) 2.6 × 10−4 m (d.) 2.6 × 10−5 m 34(34.)Two cells of equal e. m. f. and of internal resistance r1 and r2 (r1 > r2 ) are connected in series. On connecting this combination to an external resistance R, it is observed that the potential difference across the first cell becomes zero. The value of R will be (a.) r1 + r2 (b.) r1 − r2 (c.) r1+r2 2 (d.) r1−r2 2 35(35.)Four resistances 40Ω, 60Ω, 90Ω and 110Ω make the arms of a quadrilateral ABCD. Across AC is the battery circuit, the emf of the battery being 4V and internal resistance negligible. The potential difference across BD is (a.) 1V (b.) −1V (c.) −0.2Vd) 0.2V 36(36.)Two identical electric lamps marked 500 W, 220 V are connected in series and then joined to a 110 V line. The power consumed by each lamp is (a.) 125 4 W (b.) 25 4 W (c.) 225 4 W (d.) 125 W 37(37.)Two resistances when connected in parallel across a cell of negligible internal resistance consume 4 times the power they would consume when connected in series. If one resistance is 5 Ω , the other is (a.) 1 Ω (b.) 2.5 Ω (c.) 5 Ω (d.) 10 Ω 38(38.)If 96500 coulombs of electricity liberates one gram equivalent of any substance, the time taken for a current of 0.15 amperes to deposit 20mg of copper from a solution of copper sulphate is (Chemical equivalent of copper = 32) (a.) 5 min 20 sec (b.) 6 min 42 sec (c.) 4 min 40 sec (d.) 5 min 50 sec 39(39.)A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it (a.) increases, thermal velocity of the electron decreases (b.) Decreases, thermal velocity of the electron decreases (c.) increases, thermal velocity of the electron increases (d.) Decreases, thermal velocity of the electron increases 40(40.)Two bulbs when connected in parallel to a source take 60 W each. The total power consumed when they are connected in series with the same source is (a.) 15 W (b.) 30 W (c.) 60 W (d.) 120 W 41(41.)In the adjoining circuit, the e.m.f. of the cell is 2 volt and the internal resistance is negligible. The resistance of the voltmeter is 80 ohm. The reading of the voltmeter will be (a.) 0.80 volt (b.) 1.60 volt (c.) 1.33 volt (d.) 2.00 volt 42(42.)An immersion heater with electrical resistance 7 Ω is immersed in 0.1 kg of water at 20°C for 3 min. If the flow of current is 4 A, what is the final temperature of the water in ideal conditions? (Specific heat capacity of water = 4.2 × 103 Jkg) −1K −1 (a.) 28°C (b.) 48°C 90 Ω 110 Ω 40 Ω 60 Ω A C B D 4 V + – 2V 80  20  80  V