Untitled Document

Question Bank No: 1

1. A resistance coil of 60 $Ω$ is immersed in 42kg of water. What is the rise in temperature of water per minute if a steady current of 7A is made to flow through the coil

a)		${0.5}^{o} C$
b)		${1.0}^{o}$ C
c)		${10.15}^{o} C$
d)		${101.5}^{o}$ C

2. A rigid container with thermally insultated walls contains a coil of resistance 100 $Ω,$ carrying current 1A. Change in internal energy after 5 minute will be

a)		0 kJ
b)		10 kJ
c)		20 kJ
d)		30 kJ

3. If one junction of thermo couple is kept at $0^{o}$ C and its emf is given by e=at+b $t^{2}$ . Then the neutral temperature will be

a)		a/b
b)		-a/b
c)		a/2b
d)		-a/2b

4. The heat dissipated across of a resistance R and 10 volt is 20 joules/ second. What is the value of R?

a)		2 $Ω$
b)		3 $Ω$
c)		4 $Ω$
d)		5 $Ω$

5. n identical bulbs, each designed to draw a power P from a certain voltage supply, one joined in series across that supply. The total power which they will draw is

a)		nP
b)		P
c)		P/n
d)		P/ $n^{2}$

6. The volt is equal to

a)		C/q
b)		N/ $m^{2}$
c)		J/C
d)		N $m^{2}$ /C

7. A 4 $μ F$ condenser is charged to 400V and then its plates are joined through a resistance of 1k $Ω$ . The heat produced in resistance is

a)		1.28 J
b)		0.64 J
c)		0.32 J
d)		0.16 J

8. A parallel plate air capacitor has a capacitance 18 $μ F$ . If the distance between the plates is trebled and a dielectric medium is introducted the capacitance becomes 72 $μ F$ . The dielectric constant of the medium us

a)		4
b)		9
c)		12
d)		1

9. A surface encloses an electric dipole. The flux through the surface is

a)		zero
b)		positive
c)		negative
d)		infinite

10. A 60 watt bulb operates 220V supply. The current flowing through the bulb is

a)		11/3 amp
b)		3/11 amp
c)		3amp
d)		g amp

11. The maximum current that flows through a fuse wire, before it blows out, varies with its radius 'r' as

a)		$r^{1 / 2}$
b)		$r^{2 / 3}$
c)		r
d)		$r^{3 / 2}$

12. A wire of resistance 20 $Ω$ is covered with ice and a voltage of 210V is applied across the wire, the rate of melting of ice is

a)		0.85 g/s
b)		1.92 g/s
c)		6.56 g/s
d)		all of these

13. The emf in a thermo couple changes sign at 600K. If the neutral temperature is $210^{o}$ c, the temperature of cold junction is

a)		180K
b)		117 K
c)		$93^{o} C$
d)		$90^{o}$ C

14. Peltier coefficient $π$ and see beck coefficient S are related as

a)		S = $\frac{π}{T}$
b)		$π$ = $\frac{Tds}{dt}$
c)		$π = \frac{S}{T}$
d)		$\frac{ds}{dt} = \frac{T}{π}$

15. Charge carriers in the thermo couple

a)		electrons
b)		protons
c)		+ve ions
d)		-ve ions

16. Inversion temperature of a thermo couple is that the temperature of hot junction at which the emf is

a)		maximum
b)		minimum
c)		zero
d)		none of these

17. A current of 1A is passed through dilute sulphuric acid for sometine to liberate 1g of oxygen. How much hydrogen is liberated during this period

a)		2g
b)		1g
c)		0.5g
d)		0.125g

18. The electric charge for electrode deposition of 1gm equivalent of substance is

a)		One amp. per sec
b)		96500 coulomb per sec
c)		One amp. for one hour
d)		charge on one mole electrons

19. What is the density of $H_{2} {SO}_{4}$ (in g / c c) when lead acid cell is discharges?

a)		1.8
b)		2.0
c)		1.24
d)		1.18

20. Electrochemical equivalent of a substrance is the mass of the substance liberated at an electrode in half a second during electrolysis by a current of

a)		5A
b)		6A
c)		8A
d)		2A

21. An electric charge of 7.2 $\times 10^{9}$ coulombs is passed through an electrolyte of Ag ${NO}_{3}$ in 1 hour. The no. of ${Ag}^{+}$ ionsliberated during electrolysis is

a)		6.7 $\times 10^{22}$
b)		9.5 $\times 10^{22}$
c)		4.5 $\times 10^{22}$
d)		7.8 $\times 10^{22}$

22. The current capacity of a storage cell is 3Ah. The maximum current it can supply for halp hour is

a)		1.5 A
b)		3 A
c)		4.5 A
d)		6 A

23. If $R_{1}$ and $R_{2}$ are the filament resistances of a 200 W and a 100W bulb respectively both designed to run at the same voltage the

a)		$R_{2}$ is 4 times of $R_{1}$
b)		$R_{1}$ is 4 times of $R_{2}$
c)		$R_{2}$ is 2 times of $R_{1}$
d)		$R_{1}$ is 2 times of $R_{2}$

24. A voltage drop of 10V is developed across a 100 ohm resistor. How much power has the resistor dissipated

a)		10 watts
b)		1 watt
c)		100 watts
d)		0.1 watt

25. The heating element of an electric toaster has a resistance of 44 $Ω$ and is connected to 220V circuit. The heat generated in 1 minute will be

a)		17.3 $\times$ $10^{3}$ cal
b)		12.6 $\times$ $10^{3}$ cal
c)		19.68 $\times$ $10^{3}$ cal
d)		15.78 $\times$ $10^{3}$ cal

26. A coil develops heat of 800 cal/sec. when 20V is applied across its ends. The resistance of the coil is

a)		1.2 $Ω$
b)		1.4 $Ω$
c)		0.14 $Ω$
d)		0.12 $Ω$

27. What is immaterial for an electric fuse

a)		Its specific resistance
b)		Its length
c)		Its radius
d)		Current flowing throught it

28. The emf of a thermo couple whose junctions are maintained at $0^{\circ} C$ and $t^{\circ} C$ is given by e = ${a t + b t}^{2}$ , where a and b are constants. For a Ni-Cu couple a= ${16.3 \times 10}^{- 6} V / {}^{\circ}C$ and b = ${- 0.021 \times 10}^{- 6} V / {}^{\circ}{C^{2}}$ . The emf developed when the temperature of the junctions are $0^{\circ} C$ and $100^{\circ} C$ is

a)		1.42 V
b)		${1.42 \times 10}^{- 3} V$
c)		${1.42 \times 10}^{- 2} V$
d)		${1.42 \times 10}^{- 4} V$

29. An emf of 0.9mV is generated when the temperature difference between hot and cold junctions of a thermo couple is $75^{\circ}$ C. Assuming the cold junction is heated up by $15^{\circ} C$ the extent to which thermo emf will change is

a)		20%
b)		40%
c)		60%
d)		15%

30. The production of emf by maintaining a difference of temperature between the two junctions of two dissimilar metals is called

a)		Joules effect
b)		Seebeck effect
c)		Peltier effect
d)		Thomson effect

31. The temperature of the cold junction of a thermo couple is ${- 20}^{\circ} C$ and the temperature of inversion is $560^{\circ} C$ . The neutral temperature is

a)		$280^{\circ} C$
b)		$260^{\circ} C$
c)		$280^{\circ} C$
d)		$290^{\circ} C$

32. The emf of a thermo couple varies with temperature $θ$ of the hot junction as E = $14 θ - 0.02 θ^{2}$ . The neutral temperature is

a)		350K
b)		35K
c)		$350^{\circ} C$
d)		700K

33. If the cold junction of a thermo couple is at $0^{\circ} C$ and the hot junction at $100^{\circ} C$ then the relation between neutral temperature $t_{n}$ and temperature of inversion $t_{i}$ is

a)		$t_{n} = t_{i}$
b)		$t_{n} = t_{i} / 2$
c)		$t_{n} = 2 t_{i}$
d)		$t_{i} = 100^{\circ} C$

34. The thermo emf of thermo couple is

a)		independent of the nature of the material used
b)		depends on the temperature of the cold junction alone
c)		depends on the temperature of the hot junction alone
d)		depends on the temperature difference between the two junctions as well as temperature of the cold junction

35. The voltage generated by a thermo couple is given by the equation V = $α θ$ + $\frac{1}{2} β θ^{2}$ , where $α$ and $β$ are constants. Then the neutral temperature is

a)		$ρ / α$
b)		$α β$
c)		$α / 2 β$
d)		$- α / β$

36. In the circuit shown the heat produced in the 5 $Ω$ resistor due to current flowing through it is 42 ${J s}^{- 1}$ . The heat generated in the 4 $Ω$ resistor is (in ${J s}^{- 1}$ )
phtec9

a)		4.2
b)		12.6
c)		8.4
d)		16.8

37. A 200W and a 100 Wbulb both meant for operation at 220V are connected in series to a 200V supply. The power consumed by them will be

a)		33W
b)		66W
c)		100W
d)		300W

38. By how many percent will the power in a lamp decrease if the current drops by 2%

a)		2%
b)		1%
c)		3%
d)		4%

39. A 100W, 200V bulb is connected to a 160V power supply. The power consumed will be

a)		80W
b)		96W
c)		64W
d)		100W

40. One kilowatt hour is

a)		${3.6 \times 10}^{5} J$
b)		${3.6 \times 10}^{6} J$
c)		$10^{3} J$
d)		$10^{4} J$

41. Of the two bulb in a house, one glows brighter than the other. Which of the two has a higher resistance?

a)		The bright bulb
b)		The dim bulb
c)		Both have the same resistance
d)		Brightness does not depend on resistance

42. Choose the wrong statement. The amount of heat developed in a conductor is directly propotional to

a)		the square of current flowing in the conductor
b)		the resistance of the conductor
c)		time for which the current is passed
d)		resistivity of the conductor

43. You are given four bulbs of 25w, 40w, 60w and 100w. Which of them has the lowest resistance?

a)		25w
b)		40w
c)		60w
d)		100w

44. According to Joule's law, if potential difference across a resistance made of a material of resistivity $ρ$ remains constant , the heat produced in the resistor is proportional to

a)		$ρ$
b)		$ρ^{2}$
c)		$\frac{1}{ρ}$
d)		$\frac{1}{\sqrt{ρ}}$

45. In a factory 100 bulbs are connected in parallel. The rating of each bulb is 220 volts 40 watts. The current in the main wires is

a)		200/11A
b)		2/11A
c)		1/11A
d)		11/2A

46. The armature of a DC motor has 20 $Ω$ . It draws a current of 1.5A when run by 220V DC supply. The back emf of the motor is

a)		19V
b)		190V
c)		1900V
d)		250V

47. Three resistors are connected to form the sides of a triangle ABC. The resistance of the side AB is 40 $Ω$ , of the side BC 60 $Ω$ and of the side CA 100 $Ω$ . The effective resistance between the points A and B is

a)		160 $Ω$
b)		140 $Ω$
c)		40 $Ω$
d)		32 $Ω$

48. An electric iron is marked 200W, 250V. The resistance if the heater element would be approximately

a)		312.5 $Ω$
b)		62.5 $Ω$
c)		5 $Ω$
d)		8 $Ω$

49. A resistor $R_{1}$ dissipates the power 'P' when connected to a certain generator. If a certain resistance $R_{2}$ is put in series with $R_{1}$ , the power dissipated by $R_{1}$

a)		increases
b)		decreases
c)		remains same
d)		depends on the value of $R_{1}$ and $R_{2}$

50. If half of the resistance is cut off in a heater coil, the change in heating effect is that the heating effect

a)		is reduced to half
b)		is increased four times
c)		is doubled
d)		remains unchanged