Tiêu đề 19. Heating and Chemical Effects of current Easy.pdf ✅

1. One kilowatt hour is equal to (a) joules 5 36 10 (b) joules 3 36 10 (c) joules 3 10 (d) joules 5 10 2. If R1 and R2 are respectively the filament resistances of a 200 watt bulb and 100 watt bulb designed to operate on the same voltage, then (a) R1 is two times R2 (b) R2 is two times R1 (c) R2 is four times R1 (d) R1 is four times R2 3. Two electric bulbs, one of 200 volt 40 watt and the other 200 volt 100 watt are connected in a house wiring circuit (a) They have equal currents through them (b) The resistance of the filaments in both the bulbs is same (c) The resistance of the filament in 40 watt bulb is more than the resistance in 100 watt bulb (d) The resistance of the filament in 100 watt bulb is more than the resistance in 40 watt bulb 4. The two bulbs as in the above question are connected in series to a 200 volt line. Then (a) The potential drop across the two bulbs is the same (b) The potential drop across the 40 watt bulb is greater than the potential drop across the 100 watt bulb (c) The potential drop across the 100 W bulb is greater than the potential drop across the 40 W bulb (d) The potential drop across both the bulb is 200 volt 5. Forty electric bulbs are connected in series across a 220 V supply. After one bulb is fused, the remaining 39 are connected again in series across the same supply. The illumination will be (a) More with 40 bulbs than with 39 (b) More with 39 bulbs than with 40 (c) Equal in both the cases (d) In the ratio of 2 2 49 : 39 6. The material of fuse wire should have (a) A high specific resistance and high melting point (b) A low specific resistance and low melting point (c) A high specific resistance and low melting point (d) A low specific resistance and a high melting point 7. Two electric bulbs whose resistances are in the ratio of 1 : 2 are connected in parallel to a constant voltage source. The powers dissipated in them have the ratio (a) 1 : 2 (b) 1 : 1 (c) 2 : 1 (d) 1 : 4 8. A heater coil is cut into two parts of equal length and one of them is used in the heater. The ratio of the heat produced by this half coil to that by the original coil is (a) 2 : 1 (b) 1 : 2 (c) 1 : 4 (d) 4 : 1 9. Resistance of one carbon filament and one tungsten lamp are measured individually when the lamp are lit and compared with their respective resistances when cold. Which one of the following statements will be true (a) Resistance of the carbon filament lamp will increase but that of the tungsten will diminish when hot (b) Resistance of the tungsten filament lamp will increase but that of carbon will diminish when hot (c) Resistances of both the lamps will increase when hot (d) Resistances of both the lamps will decrease when hot 10. The mechanism of the heat produced in a conductor when an electric current flows through it, can be explained on the basis of (a) Viscosity (b) Friction (c) Free electron theory (d) Gauss's theorem 11. Two electric bulbs whose resistances are in the ratio of 1 : 2 are connected in series. The powers dissipated in them have the ratio (a) 1 : 2 (b) 2 : 1 (c) 1 : 1 (d) 1 : 4 12. You are given a resistance wire of length 50 cm and a battery of negligible resistance. In which of the following cases is largest amount of heat generated (a) When the wire is connected to the battery directly (b) When the wire is divided into two parts and both the parts connected to the battery in parallel (c) When the wire is divided into four parts and all the four connected to the battery in parallel (d) When only half the wire is connected to the battery 13. What is immaterial for an electric fuse wire (a) Its specific resistance (b) Its radius (c) Its length (d) Current flowing through it 14. The electric bulbs have tungsten filaments of same length. If one of them gives 60 watt and other 100 watt, then (a) 100 watt bulb has thicker filament (b) 60 watt bulb has thicker filament (c) Both filaments are of same thickness (d) It is possible to get different wattage unless the lengths are different 15. Three equal resistors connected in series across a source of e.m.f. together dissipate 10 watt. If the same resistors are connected in parallel across the same e.m.f., then the power dissipated will be (a) 10 watt (b) 30 watt (c) 10/3 watt (d) 90 watt
16. How much energy in kilowatt hour is consumed in operating ten 50 watt bulbs for 10 hours per day in a month (30 days). (a) 1500 (b) 5,000 (c) 15 (d) 150 17. (1) The product of a volt and a coulomb is a joule. (2) The product of a volt and an ampere is a joule/second. (3) The product of volt and watt is horse power. (4) Watt-hour can be measured in terms of electron volt. State if (a) All four are correct (b) (1), (2) and (4) are correct (c) (1) and (3) are correct (d) (3) and (4) are correct 18. A 25 W, 220 V bulb and a 100 W, 220 V bulb are connected in parallel across a 440 V line (a) Only 100 watt bulb will fuse (b) Only 25 watt bulb will fuse (c) Both bulbs will fuse (d) None of the bulbs will fuse 19. Two electric lamps of 40 watt each are connected in parallel. The power consumed by the combination will be (a) 20 watt (b) 60 watt (c) 80 watt (d) 100 watt 20. Two heating coils, one of fine wire and the other of thick wire of the same material and of the same length are connected in series and in parallel. Which of the following statement is correct (a) In series fine wire liberates more energy while in parallel thick wire will liberate more energy (b) In series fine wire liberates less energy while in parallel thick wire will liberate more energy (c) Both will liberate equally (d) In series the thick wire will liberate more while in parallel it will liberate less energy 21. An electric bulb is rated 220 volt and 100 watt. Power consumed by it when operated on 110 volt is (a) 50 watt (b) 75 watt (c) 90 watt (d) 25 watt 22. A 25 watt, 220 volt bulb and a 100 watt, 220 volt bulb are connected in series across a 220 volt lines. Which electric bulb will glow more brightly (a) 25 watt bulb (b) 100 watt bulb (c) First 25 watt and then 100 watt (d) Both with same brightness 23. A resistor R1 dissipates the power P when connected to a certain generator. If the resistor R2 is put in series with R1 , the power dissipated by R1 (a) Decreases (b) Increases (c) Remains the same (d) Any of the above depending upon the relative values of R1 and R2 24. An electric fan and a heater are marked as 100 watt, 220 volt and 1000 watt, 220 volt respectively. The resistance of the heater is (a) Zero (b) Greater than that of the fan (c) Less than that of the fan (d) Equal to that of the fan 25. According to Joule's law, if the potential difference across a conductor having a material of specific resistance remains constant, then the heat produced in the conductor is directly proportional to (a)  (b) 2  (c)  1 (d)  1 26. Two heater wires of equal length are first connected in series and then in parallel. The ratio of heat produced in the two cases is (a) 2 : 1 (b) 1 : 2 (c) 4 : 1 (d) 1 : 4 27. Two bulbs of equal wattage, one having carbon filament and the other having a tungsten filament are connected in series to the mains, then (a) Both bulbs glow equally (b) Carbon filament bulb glows more (c) Tungsten filament bulbs glows more (d) Carbon filament bulb glows less 28. Two identical heaters rated 220 volt, 1000 watt are placed in series with each other across 220 volt lines. If resistance do not change with temperature, then the combined power is (a) 1000 watt (b) 2000 watt (c) 500 watt (d) 4000 watt 29. A 25 watt, 220 volt bulb and a 100 watt, 220 volt bulb are connected in parallel across a 220 volt line. Which bulb will glow more brightly (a) 25 watt bulb (b) 100 watt bulb (c) Both will have same brightness (d) First 25 watt then 100 watt 30. If two bulbs of wattage 25 and 100 respectively each rated at 220 volt are connected in series with the supply of 440 volt,

(d) Without voltage, cannot be calculated 47. The brightness of a bulb will be reduced, if a resistance is connected in (a) Series with it (b) Parallel with it (c) Series or parallel with it (d) Brightness of the bulb cannot be reduced 48. A 100 watt bulb working on 200 volt and a 200 watt bulb working on 100 volt have (a) Resistances in the ratio of 4 : 1 (b) Maximum current ratings in the ratio of 1 : 4 (c) Resistances in the ratio of 2 : 1 (d) Maximum current ratings in the ratio of 1 : 2 49. There are two electric bulbs of 40 W and 100 W. Which one will be brighter when first connected in series and then in parallel, (a) 40 W in series and 100 W in parallel (b) 100 W in series and 40 W in parallel (c) 40 W both in series and parallel will be uniform (d) 100 W both in series and parallel will be uniform 50. Two resistances R1 and R2 when connected in series and parallel with 120 V line, power consumed will be 25 W and 100 W respectively. Then the ratio of power consumed by R1 to that consumed by R2 will be (a) 1 : 1 (b) 1 : 2 (c) 2 : 1 (d) 1 : 4 51. A 220 volt and 800 watt electric kettle and three 220 volt and 100 watt bulbs are connected in parallel. On connecting this combination with 220 volt electric supply, the total current will be (a) 0.15 ampere (b) 5.0 ampere (c) 5.5 ampere (d) 6.9 ampere 52. You are given three bulbs of 25, 40 and 60 watt. Which of them has lowest resistance (a) 25 watt bulb (b) 40 watt bulb (c) 60 watt bulb (d) Information is insufficient 53. The value of internal resistance of an ideal cell is (a) Zero (b) 0.5  (c) 1 (d) Infinity 54. Electric power is transmitted over long distances through conducting wires at high voltage because (a) High voltage travels faster (b) Power loss is large (c) Power loss is less (d) Generator produced electrical energy at a very high voltage 55. A coil develops heat of 800 cal/sec. When 20 volts is applied across its ends. The resistance of the coil is (1 cal = 4.2 joule) (a) 1.2  (b) 1.4  (c) 0.12  (d) 0.14  56. Resistances R1 and R2 are joined in parallel and a current is passed so that the amount of heat liberated is H1 and H 2 respectively. The ratio 2 1 H H has the value (a) 1 2 R R (b) 2 1 R R (c) 2 2 2 1 R R (d) 2 1 2 2 R R 57. The internal resistance of a primary cell is 4 ohm. It generates a current of 0.2 amp in an external resistance of 21 ohm. The rate at which chemical energy is consumed in providing the current is (a) 0.42 J / s (b) 0.84 J / s (c) 5 J / s (d) 1 J / s 58. A heating coil is labelled 100 W, 220 V. The coil is cut in half and the two pieces are joined in parallel to the same source. The energy now liberated per second is (a) 200 J (b) 400 J (c) 25 J (d) 50 J 59. Which of the following is not a correct statement (a) Resistivity of electrolytes decreases on increasing temperature (b) Resistance of mercury falls on decreasing its temperature (c) When joined in series a 40 W bulb glows more than a 60 W bulb (d) Resistance of 40 W bulb is less than the resistance of 60 W bulb 60. Three light bulbs of 40 W, 60 W and 100 W are connected in series with 220 V source. Which one of the bulbs will glow brightest (a) 40 W (b) 60 W (c) 100 W (d) All with the same brightness 61. The energy consumed in 1 kilowatt electric heater in 30 seconds will be (a) J 2 6 10 (b) J 7 4.99 10 (c) J 6 9.8 10 (d) J 4 3 10