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question_answer1)
The resistance of the filament of an electric bulb changes with temperature. If an electric bulb rated 220 volt and 100 watt is connected \[(220\times .8)\] volt sources, then the actual power would be [CPMT 1989]
A)
\[100\times 0.8\,watt\] done
clear
B)
\[100\times {{(0.8)}^{2}}watt\] done
clear
C)
Between \[100\times 0.8\]watt and 100 watt done
clear
D)
Between \[100\times {{(0.8)}^{2}}watt\] and \[100\times 0.8\]watt done
clear
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question_answer2)
An immersion heater is rated 836 watt. It should heat 1 litre of water from \[10{}^\circ C\] to \[40{}^\circ C\] in about [AIEEE 2004]
A)
200 sec done
clear
B)
150 sec done
clear
C)
836 sec done
clear
D)
418 sec done
clear
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question_answer3)
In the circuit shown in figure, the heat produced in 5 ohm resistance is 10 calories per second. The heat produced in 4 resistance is [IIT 1981; UPSEAT 2002]
A)
1 cal / sec done
clear
B)
2 cal/sec done
clear
C)
3 cal / sec done
clear
D)
4 cal/sec done
clear
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question_answer4)
A house is served by 220 V supply line in a circuit protected by a 9 ampere fuse. The maximum number of 60 W lamps in parallel that can be turned on, is
A)
44 done
clear
B)
20 done
clear
C)
22 done
clear
D)
33 done
clear
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question_answer5)
Water boils in an electric kettle in 15 minutes after switching on. If the length of the heating wire is decreased to \[2/3\] of its initial value, then the same amount of water will boil with the same supply voltage in [MP PMT 1994]
A)
15 minutes done
clear
B)
12 minutes done
clear
C)
10 minutes done
clear
D)
8 minutes done
clear
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question_answer6)
In the circuit as shown in the figure, the heat produced by 6 ohm resistance due to current flowing in it is 60 calorie per second. The heat generated across 3 ohm resistance per second will be [MP PET 1996]
A)
30 calorie done
clear
B)
60 calorie done
clear
C)
100 calorie done
clear
D)
120 calorie done
clear
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question_answer7)
The resistance of a heater coil is 110 ohm. A resistance R is connected in parallel with it and the combination is joined in series with a resistance of 11 ohm to a 220 volt main line. The heater operates with a power of 110 watt. The value of R in ohm is [ISM Dhanbad 1994]
A)
12.22 done
clear
B)
24.42 done
clear
C)
Negative done
clear
D)
That the given values are not correct done
clear
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question_answer8)
A 500 W heating unit is designed to operate from a 115 volt line. If the line voltage drops to 110 volt, the percentage drop in heat output will be [ISM Dhanbad 1994]
A)
10.20% done
clear
B)
8.1% done
clear
C)
8.6% done
clear
D)
7.6% done
clear
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question_answer9)
A heater of 220 V heats a volume of water in 5 minute time. A heater of 110 V heats the same volume of water in [AFMC 1993]
A)
5 minutes done
clear
B)
8 minutes done
clear
C)
10 minutes done
clear
D)
20 minutes done
clear
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question_answer10)
An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from room temperature\[20{}^\circ C\]? The temperature of boiling water is \[100{}^\circ C\] [RPET 1996]
A)
6.4 minutes done
clear
B)
6.3 minutes done
clear
C)
12.6 minutes done
clear
D)
12.8 minutes done
clear
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question_answer11)
If a wire of resistance \[20\,\Omega \] is covered with ice and a voltage of 210 V is applied across the wire, then the rate of melting of ice is [AFMC 1997]
A)
\[0.85\,g/s\] done
clear
B)
\[1.92\,g/s\] done
clear
C)
\[6.56\,g/s\] done
clear
D)
All of these done
clear
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question_answer12)
Four identical electrical lamps are labelled 1.5V, 0.5A which describes the condition necessary for them to operate at normal brightness. A 12V battery of negligible internal resistance is connected to lamps as shown, then [UPSEAT 2001]
A)
The value of R for normal brightness of each lamp is (3/4) W done
clear
B)
The value of R for normal brightness of each lamp is (21/4) W done
clear
C)
Total power dissipated in circuit when all lamps are normally bright is 24W done
clear
D)
Power dissipated in R is 21W when all lamps are normally bright done
clear
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question_answer13)
A 100 W bulb B1, and two 60-W bulbs B2 and B3, are connected to a 250 V source, as shown in the figure. Now W1, W2 and W3 are the output powers of the bulbs B1, B2 and B3, respectively. Then [IIT-JEE (Screening) 2002]
A)
\[{{W}_{1}}>{{W}_{2}}={{W}_{3}}\] done
clear
B)
\[{{W}_{1}}>{{W}_{2}}>{{W}_{3}}\] done
clear
C)
\[{{W}_{1}}<{{W}_{2}}={{W}_{3}}\] done
clear
D)
\[{{W}_{1}}<{{W}_{2}}<{{W}_{3}}\] done
clear
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question_answer14)
The three resistance of equal value are arranged in the different combinations shown below. Arrange them in increasing order of power dissipation [IIT-JEE (Screening) 2003] I.
II.
III.
IV.
A)
III < II < IV < I done
clear
B)
II < III < IV < I done
clear
C)
I < IV < III < II done
clear
D)
I < III < II < IV done
clear
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question_answer15)
Silver and copper voltameter are connected in parallel with a battery of e.m.f. 12 V. In 30 minutes, 1 gm of silver and 1.8 gm of copper are liberated. The power supplied by the battery is [IIT 1975]
A)
24.13 J/sec done
clear
B)
2.413 J/sec done
clear
C)
0.2413 J/sec done
clear
D)
2413 J/sec \[({{Z}_{Cu}}=6.6\times {{10}^{-4}}gm/C\] and \[{{Z}_{Ag}}=11.2\times {{10}^{-4}}\,gm/C)\] done
clear
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question_answer16)
A silver voltameter of resistance 2 ohm and a 3 ohm resistor are connected in series across a cell. If a resistance of 2 ohm is connected in parallel with the voltameter, then the rate of deposition of silver [EAMCET 1983]
A)
Decreases by 25% done
clear
B)
Increases by 25% done
clear
C)
Increases by 37.5% done
clear
D)
Decreases by 37.5% done
clear
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question_answer17)
The expression for thermo e.m.f. in a thermocouple is given by the relation\[E=40\,\theta -\frac{{{\theta }^{2}}}{20}\], where \[\theta \] is the temperature difference of two junctions. For this, the neutral temperature will be [AMU (Engg.) 2000]
A)
\[100{}^\circ C\] done
clear
B)
\[200{}^\circ C\] done
clear
C)
\[300{}^\circ C\] done
clear
D)
\[400{}^\circ C\] done
clear
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question_answer18)
For copper-iron (Cu-Fe) couple, the thermo e.m.f. (temperature of cold junction\[=0{}^\circ C\]) is given by\[E=(14\theta -0.02{{\theta }^{2}})\mu V\]. The neutral temperature will be
A)
\[350{}^\circ C\] done
clear
B)
350 K done
clear
C)
\[560{}^\circ C\] done
clear
D)
560 K done
clear
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question_answer19)
One junction of a certain thermoelectric couple is at a fixed temperature \[{{T}_{r}}\] and the other junction is at temperature T. The thermo electromotive force for this is expressed by \[E=K(T-{{T}_{r}})\left[ {{T}_{0}}-\frac{1}{2}(T+{{T}_{r}}) \right]\]. At temperature \[T=\frac{1}{2}{{T}_{0}}\], the thermoelectric power is [MP PMT 1994]
A)
\[\frac{1}{2}K{{T}_{0}}\] done
clear
B)
\[K{{T}_{0}}\] done
clear
C)
\[\frac{1}{2}KT_{0}^{2}\] done
clear
D)
\[\frac{1}{2}K{{({{T}_{0}}-{{T}_{r}})}^{2}}\] done
clear
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question_answer20)
The temperature of the cold junction of thermo‑couple is \[0{}^\circ C\] and the temperature of hot junction is \[T{}^\circ C\]. The e.m.f. is \[E=16T-0.04{{T}^{2}}\mu \] volts. The temperature of inversion is [EAMCET 1994]
A)
\[200{}^\circ C\] done
clear
B)
\[400{}^\circ C\] done
clear
C)
\[100{}^\circ C\] done
clear
D)
\[300{}^\circ C\] done
clear
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question_answer21)
The temperature of the cold junction of a thermocouple is \[{{0}^{o}}C\] and temperature of the hot junction is \[{{T}^{o}}C.\] The thermo e.m.f. is given by the relation \[E=AT-\frac{1}{2}B{{T}^{2}}\] (where A = 16 and B = 0.08). The temperature of inversion is [AIIMS 2001]
A)
\[{{100}^{o}}C\] done
clear
B)
\[{{300}^{o}}C\] done
clear
C)
\[{{400}^{o}}C\] done
clear
D)
\[{{500}^{o}}C\] done
clear
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question_answer22)
The thermo e.m.f. of a thermo-couple is \[25\mu V{{/}^{o}}C\] at room temperature. A galvanometer of 40 ohm resistance, capable of detecting current as low as \[{{10}^{-5}}A,\] is connected with the thermocouple. The smallest temperature difference that can be detected by this system is [AIEEE 2003]
A)
\[{{20}^{o}}C\] done
clear
B)
\[{{16}^{o}}C\] done
clear
C)
\[{{12}^{o}}C\] done
clear
D)
\[{{8}^{o}}C\] done
clear
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question_answer23)
An electric bulb rated for 500 watts at 100 volts is used in a circuit having a 200-volt supply. The resistance R that must be put in series with the bulb, so that the bulb draws 500 W is
A)
\[10\,\Omega \] done
clear
B)
\[20\,\Omega \] done
clear
C)
D)
\[50\,\Omega \] done
clear
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question_answer24)
A thermo couple develops \[200\,\mu \,V\] between \[{{0}^{o}}C\] and \[{{100}^{o}}C.\] If it develops \[64\,\,\mu \,V\] and \[76\,\mu \,V\] respectively between \[({{0}^{o}}C-{{32}^{o}}C)\] and \[({{32}^{o}}C-{{70}^{o}}C)\]then what will be the thermo emf it develops between \[{{70}^{o}}C\] and \[{{100}^{o}}C\]
A)
\[65\,\,\mu \,V\] done
clear
B)
\[60\,\,\mu V\] done
clear
C)
\[55\,\,\mu V\] done
clear
D)
\[50\,\,\mu V\] done
clear
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question_answer25)
A thermo couple is formed by two metals X and Y metal X comes earlier to Y in Seebeck series. If temperature of hot junction increases beyond the temperature of inversion. Then direction of current in thermocouple will so
A)
X to Y through cold junction done
clear
B)
X to Y through hot junction done
clear
C)
Y to X through cold junction done
clear
D)
Both (b) and (c) done
clear
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question_answer26)
Peltier co-efficient of a thermo couple is 2 nano volts. How much heat is developed at a junction if 2.5 amp current flows for 2 minute
A)
6 ergs done
clear
B)
\[6\times {{10}^{-7}}\,ergs\] done
clear
C)
16 ergs done
clear
D)
\[6\times {{10}^{-3}}\,\,erg\] done
clear
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question_answer27)
Resistance of a voltameter is \[2\,\Omega ,\] it is connected in series to a battery of 10 V through a resistance of \[3\,\Omega \]. In a certain time mass deposited on cathode is 1 gm. Now the voltameter and the \[3\,\Omega \] resistance are connected in parallel with the battery. Increase in the deposited mass on cathode in the same time will be
A)
0 done
clear
B)
1.5 gm done
clear
C)
2.5 gm done
clear
D)
2 gm done
clear
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question_answer28)
A current of 1.5 A flows through a copper voltameter. The thickness of copper deposited on the electrode surface of area \[50\,c{{m}^{2}}\] in 20 minutes will be (Density of copper = 9000 \[kg/{{m}^{3}}\] and E.C.E. of copper = 0.00033 g/C)
A)
\[2.6\times {{10}^{-5}}m\] done
clear
B)
\[2.6\times {{10}^{-4}}m\] done
clear
C)
\[1.3\times {{10}^{-5}}m\] done
clear
D)
\[1.3\times {{10}^{-4}}m\] done
clear
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question_answer29)
An ammeter, suspected to give inaccurate reading, is connected in series with a silver voltameter. The ammeter indicates 0.54 A. A steady current passed for one hour deposits 2.0124 gm of silver. If the E.C.E. of silver is \[1.118\times {{10}^{-3}}\,gm{{C}^{-1}},\] then the error in ammeter reading is
A)
+ 0.04 A done
clear
B)
+ 0.02 A done
clear
C)
? 0.03 A done
clear
D)
? 0.01 A done
clear
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question_answer30)
If 1 A of current is passed through \[CuS{{O}_{4}}\] solution for 10 seconds, then the number of copper ions deposited at the cathode will be about
A)
\[1.6\times {{10}^{19}}\] done
clear
B)
\[3.1\times {{10}^{19}}\] done
clear
C)
\[4.8\times {{10}^{19}}\] done
clear
D)
\[6.2\times {{10}^{19}}\] done
clear
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question_answer31)
A silver and a copper voltmeters are connected in parallel across a 6 volt battery of negligible resistance. In half an hour, 1 gm of copper and 2 gm of silver are deposited. The rate at which energy is supplied by the battery will approximately be (Given E.C.E. of copper \[=3.294\times {{10}^{-4}}\,g/C\] and E.C.E. of silver \[=1.118\times {{10}^{-3}}\,g/C)\]
A)
64 W done
clear
B)
32 W done
clear
C)
96 W done
clear
D)
16 W done
clear
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question_answer32)
A thermocouple of resistance \[1.6\,\Omega \] is connected in series with a galvanometer of \[8\,\Omega \] resistance. The thermocouple develops and e.m.f. of \[10\mu V\] per degree temperature difference between two junctions. When one junction is kept at \[{{0}^{o}}C\] and the other in a molten metal, the galvanometer reads 8 millivolt. The temperature of molten metal, when e.m.f. varies linearly with temperature difference, will be
A)
\[{{960}^{o}}C\] done
clear
B)
\[{{1050}^{o}}C\] done
clear
C)
\[{{1275}^{o}}C\] done
clear
D)
\[{{1545}^{o}}C\] done
clear
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question_answer33)
The emf of a thermocouple, one junction of which is kept at \[{{0}^{o}}C,\] is given by \[e=at+b{{t}^{2}}\] the Peltier co-efficient will be
A)
\[(t+273)\,\,(a+2bt)\] done
clear
B)
\[(t+273)\,\,(a-2bt)\] done
clear
C)
\[(t-273)\,\,(a-2bt)\] done
clear
D)
\[(t-273)\,\,(a-2bt)\] done
clear
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question_answer34)
A coil of wire of resistance \[50\,\Omega \] is embedded in a block of ice. If a potential difference of 210 V is applied across the coil, the amount of ice melted per second will be
A)
4.12 gm done
clear
B)
4.12 kg done
clear
C)
3.68 kg done
clear
D)
2.625 gm done
clear
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question_answer35)
The same mass of copper is drawn into two wires 1 mm and 2 mm thick. Two wires are connected in series and current is passed through them. Heat produced in the wire is in the ratio
A)
2 : 1 done
clear
B)
1 : 16 done
clear
C)
4 : 1 done
clear
D)
16 : 1 done
clear
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question_answer36)
The temperature of hot junction of a thermo-couple changes from \[{{80}^{o}}C\] to \[{{100}^{o}}C.\] The percentage change in thermoelectric power is
A)
8% done
clear
B)
10% done
clear
C)
20% done
clear
D)
25% done
clear
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question_answer37)
A thermo couple uses Bismuth and Tellurium as the dissimilar metals. The sensitivity of bismuth is \[-\,72\mu \,V{{/}^{o}}C\] and that of the tellurium is \[500\mu \,\,V{{/}^{o}}C\]. If the difference between hot and cold junction is \[{{100}^{o}}C,\] then the maximum output will be
A)
\[50\,\,mV\] done
clear
B)
\[7.2\,\,mV\] done
clear
C)
\[42.8\,\,mV\] done
clear
D)
\[57.2\,\,mV\] done
clear
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question_answer38)
Three wires of copper, iron and nickel are joined to form three junctions as shown in Fig. When the temperature of junction 1 is kept \[{{50}^{o}}C\] with the other two junctions at \[{{0}^{o}}C\], the sensitive galvanometer gives a deflection of 14 divisions. When the temperature of junction 3 is kept \[{{50}^{o}}C,\]with the other two junctions at \[{{0}^{o}}C,\] the galvanometer gives a deflection of 11 divisions. Then the deflection given by the galvanometer, when temperature of the junction 2 is kept at \[{{50}^{o}}C,\] with the other two junctions at \[{{0}^{o}}C,\] will be
A)
3 div done
clear
B)
11 div done
clear
C)
14 div done
clear
D)
25 div done
clear
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question_answer39)
The wiring of a house has resistance \[6\,\Omega .\] A 100 W bulb is glowing. If a geyser of 1000 W is switched on, the change in potential drop across the bulb is nearly [MNR 1998]
A)
Nil done
clear
B)
23 V done
clear
C)
32 V done
clear
D)
12 V done
clear
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question_answer40)
A 12 V lead accumulator is being charged using 24 V supply with an external resistance \[2\,\Omega \]. The internal resistance of the accumulator is\[1\,\Omega \]. Find the time in which it will store 360 W-hour energy.
A)
1 hr done
clear
B)
7.5 hr done
clear
C)
10 hr done
clear
D)
None of these done
clear
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question_answer41)
In a Ag voltameter 2.68 gm of silver is deposited in 10 min. The heat developed in \[20\,\Omega \] resistor during the same period will be
A)
192 kJ done
clear
B)
192 J done
clear
C)
200 J done
clear
D)
132 kJ done
clear
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question_answer42)
The thermo e.m.f. of a thermocouple varies with the temperature \[\theta \] of the hot junction as \[E=a\theta +b{{\theta }^{2}}\] in volts where the ratio a/b is \[{{700}^{o}}C.\] If the cold junction is kept at \[{{0}^{o}}C,\] then the neutral temperature is [AIEEE 2004]
A)
\[{{700}^{o}}C\] done
clear
B)
\[{{350}^{o}}C\] done
clear
C)
\[{{1400}^{o}}C\] done
clear
D)
No neutral temperature is possible for this thermocouple done
clear
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question_answer43)
In the following circuit, 5 W resistor develops 45 J/s due to current flowing through it. The power developed per second across 12 W resistor is [AMU (Engg.) 1999]
A)
16 W done
clear
B)
192 W done
clear
C)
36 W done
clear
D)
64 W done
clear
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question_answer44)
Water of volume 2 litre in a container is heated with a coil of 1 kW at 27 oC. The lid of the container is open and energy dissipates at rate of 160 J/s. In how much time temperature will rise from 27oC to 77oC [Given specific heat of water is 4.2 kJ/kg] [IIT-JEE (Screening) 2005]
A)
8 min 20 s done
clear
B)
6 min 2 s done
clear
C)
7 min done
clear
D)
14 min done
clear
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question_answer45)
For ensuring dissipation of same energy in all three resistors \[({{R}_{1}},\,{{R}_{2}},\,{{R}_{3}})\] connected as shown in figure, their values must be related as ] [AIIMS 2005]
A)
\[{{R}_{1}}={{R}_{2}}={{R}_{3}}\] done
clear
B)
\[{{R}_{2}}={{R}_{3}}\]and \[{{R}_{1}}=4{{R}_{2}}\] done
clear
C)
\[{{R}_{2}}={{R}_{3}}\]and \[{{R}_{1}}=\frac{1}{4}{{R}_{2}}\] done
clear
D)
\[{{R}_{1}}={{R}_{2}}+{{R}_{3}}\] done
clear
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