Untitled Document

Question Bank No: 2

1. The masses of three wires of copper are in the ratio of 1 : 3 : 5. And their length are in the ratio of 5 : 3 : 1. The ratio of their electrical resistance is

a)		1 : 1 : 1
b)		1 : 3 : 5
c)		5 : 3 : 1
d)		125 : 15 : 1

2. The magnitude of the temperature coefficient of resistivity is often quite large for a semiconductor. This fact has been used to manufacture thermometers which can detect temperature change of the order of $10^{- 3}$ degree C. Such a device is called a

a)		Semi-conductor thermometer
b)		Voltmeter
c)		Thermistor
d)		Potentiometer

3. The V-I graph for a conductor at temperature $T_{1}$ and $T_{2}$ are as shown in the figure. The term ( $T_{2} - T_{1}$ ) is propotional to
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a)		Cos $2 θ$
b)		Sin $2 θ$
c)		Cot $2 θ$
d)		Tan $2 θ$

4. Superconductivity is observed because of

a)		Independent electron which can not be deflected by ionic vibrations
b)		Mutually coherent electron cloud which cannot deflected by ionic vibrations
c)		Ionic vibrations that cause deflections, cease leading to nearly zero resistivity
d)		Reasons are not yet known

5. The phenomenon of superconductivity was first discovered by

a)		Ohm
b)		H. Kammerlling Onnes
c)		Andre M. Ampere
d)		Kirchoff

6. For which of the following dependence of drift velocity $v_{d}$ on electric field E, is the Ohm's law obeyed?

a)		$v_{d} \propto E^{2}$
b)		$v_{d} \propto E^{1 / 2}$
c)		$v_{d} \propto E$
d)		$v_{d}$ is independent of E

7. A metallic block has no potential difference applied across it, then the mean velocity of free electrons is ( T = temperature in kelvin)

a)		Propotional to T
b)		Propotional to $\sqrt{T}$
c)		Zero
d)		Finite but independent of T

8. In a household, at an instant of time only a 50 watt lamp and a 50 watt electrical appliance are on, both working on the 200 volt domestic supply. The current passing through the electric meter in the house is

a)		20 A
b)		42 A
c)		30 A
d)		0.5 A

9. A moving coil galvanometer has a resistance of 900 $Ω$ . In order to send only 10 % of the main current through this galvanometer, the resistance of the required shunt is

a)		0.9 $Ω$
b)		100 $Ω$
c)		405 $Ω$
d)		90 $Ω$

10. A potentiometer wire has length 10 m and resistance 20 $Ω$ . A 2.5 V battery of negligible internal resistance is connected across the wire with an 80 $Ω$ series resistance. The potential gradient on the wire will be

a)		2.5 $\times 10^{- 4}$ V/cm
b)		0.62 $\times 10^{- 4}$ V/cm
c)		1 $\times 10^{- 5}$ V/cm
d)		5 $\times 10^{- 5}$ V/cm

11. A steady current flows in a metallic conductor of non-uniform cross section. Then which of the following quantities are constant along the conductor?

a)		Current, current density
b)		Current
c)		Current, current density, electric field
d)		Current, current density, electric field, drift speed

12. Two conductors made of the same material have lengths L and 2L, but have equal resistance. The two are connected in series in a circuit in which current is flowing. Which of the following is correct?

a)		The p.d across the two conductors is the same
b)		The electron drift velocity is larger in the conductor of length 2L
c)		The electric field in the first conductor is twice that in the second
d)		The electric field in the second conductor is twice that in the first

13. Two wires of equal length and of materials x and y have equal resistance. The ratio of the radii of the two wires is 1: 2. The ratio of the resistivities of x and y will be

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

14. In the figure given the resistance between A and B is (in ohms)
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a)		24/19
b)		19/24
c)		18/24
d)		10/12

15. Look at the figure. The equivalent resistance between A and D is
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a)		15 $Ω$
b)		5 $Ω$
c)		10 $Ω$
d)		25 $Ω$

16. A battery of e.m.f 2V and internal resistance 2 $Ω$ is connected to a 10m potentiometer wire of resistance 18 $Ω$ . The length of the wire balancing a Daniel cell of e.m.f 1.08 V is

a)		5.5 m
b)		6m
c)		6.5 m
d)		5m

17. The area of cross section of a wire is $10^{- 7} m^{2}$ and the number density of free electrons in the wire is ${2 \times 10}^{28} / m^{3}$ . When the current in the wire is 3.2 A, the drift velocity of the electron (in ${ms}^{- 1}$ )

a)		0.001
b)		0.01
c)		0.0001
d)		0.1

18. A resistance R is connected to a cell of emf and internal resistance r through an ammeter of negligible resistance as shown in the figure. When R = 4 $Ω$ , the ammaeter reads 4A and when R = 9 $Ω$ the ammeter reads 2A. The internal resistance of the cell is
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a)		1 $Ω$
b)		2 $Ω$
c)		3 $Ω$
d)		1.5 $Ω$

19. A battery of e.m.f E and internal resistance r is connected to an external resistancce r. The terminal p.d of the battery

a)		2E
b)		E
c)		E/2
d)		E/3

20. In a H-atom the electron make ${6.6 \times 10}^{15}$ rps round the nucleus in an orbit of radius 0.5 $A^{\circ}$ . The equialent current is nearly c = ${1.6 \times 10}^{- 19}$ c
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a)		$10^{2} A$
b)		$10^{- 3} A$
c)		$10^{- 4} A$
d)		$10^{- 5} A$

21. Each of the resistances in the network is R. The resistance between terminals A and B is
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a)		R
b)		2R
c)		3R
d)		R/3

22. In the following network the effective resistance between A and B is $[R = 3 Ω]$
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a)		12 $Ω$
b)		4 $Ω$
c)		4/3 $Ω$
d)		3/4 $Ω$

23. If the resistance of a circuit having 12 V source is increased by 4 $Ω$ , the current drops by 0.5A. The original resistance is

a)		12 $Ω$
b)		8 $Ω$
c)		6 $Ω$
d)		4.5 $Ω$

24. Two wires of the same material have the same length but their cross sections are in the ratio 3 : 1. They are joined in series. The resistance of the thicker wire is 10 $Ω$ . The total resistance of the combination in ohm is

a)		7.5 $Ω$
b)		40 $Ω$
c)		5/2 $Ω$
d)		100 $Ω$

25. In the given circuit the resistance between A and C is
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a)		20 $Ω$
b)		30 $Ω$
c)		60 $Ω$
d)		0.01 $Ω$

26. Two identical resistances each 1 $Ω$ are joined in parallel. The combination has a resistance

a)		10 $Ω$
b)		1 $Ω$
c)		0.1 $Ω$
d)		0.01 $Ω$

27. n similar resistances each of resistance r when connected in parallel has an effective resistance R. When they are connected in series the effective resistance is

a)		nR
b)		$n^{2} R$
c)		$\frac{R}{n}$
d)		$\frac{R}{n^{2}}$

28. In a wheatstone bridge P = 9 $Ω$ ,Q = 11 $Ω$ , R = 4 $Ω$ and S = 6 $Ω$ in an order. How much resistance must be put in parallel to resistance S to balance the bridge.

a)		$\frac{36}{5} Ω$
b)		$\frac{44}{9} Ω$
c)		24 $Ω$
d)		26.4 $Ω$

29. In which of the following substances the resistance decreases with increases in temperature

a)		carbon
b)		contantan
c)		copper
d)		silver

30. When the temperature of a metallic conductor increases its resistance

a)		always increases
b)		always decreases
c)		remains the same
d)		may increase or decrease

31. Potentio meter is preferred to a voltmeter to measure voltage in a circuit because

a)		potentio meter is handy compared to voltmeter to measure voltage in a circuit
b)		potentio meter is cheaper
c)		no current is drawn by a potentio meter during measurement
d)		none of the above

32. Three resistances 1 $Ω$ each are connected to form a triangle. The resistance between any two corners will be

a)		$\frac{2}{3} Ω$
b)		$\frac{4}{2} Ω$
c)		$\frac{1}{3} Ω$
d)		$\frac{3}{2} Ω$

33. A wire of resistance 3 $Ω$ is stretched to twice its original length. The resistance is

a)		3 $Ω$
b)		6 $Ω$
c)		9 $Ω$
d)		12 $Ω$

34. Which of the following is best material for making connecting wires

a)		Tungesten
b)		Constantan
c)		Nichsome
d)		Copper

35. The effective resistance R is obtained by connecting n identical resistors each of resistance r in series. When these resistors are connected in parallel the effective resistance of the combination is

a)		$\frac{n^{2}}{R}$
b)		$\frac{R}{n^{2}}$
c)		${Rn}^{2}$
d)		${Rr}^{2}$

36. A wire has a resistance 16 $Ω$ . It is bent in the form of a circle. The effective resistance between two points on any diameter of the circle is

a)		16 $Ω$
b)		8 $Ω$
c)		4 $Ω$
d)		2 $Ω$

37. The resistance of 0.01 $Ω$ is connected to a resistance of one kiloohm in parallel. The resistance of the combination will be

a)		100 $Ω$
b)		1000.01 $Ω$
c)		10 $Ω$
d)		0.01 $Ω$

38. The colour rings of a carbon resistor are Green, Grey and Blue. The resistance of the resistor is

a)		58 M $Ω$
b)		586 $Ω$
c)		568 $Ω$
d)		5.8 k $Ω$

39. The area of cross section of a of a copper wire is $3 \times 10^{- 6} m^{2}$ . A current of 4.2A flows through it. The current density in the wire in A/ $m^{2}$ is

a)		$1.4 \times 10^{- 6}$
b)		$2.8 \times 10^{- 6}$
c)		$0.7 \times 10^{- 6}$
d)		$1.4 \times 10^{6}$

40. If a copper wire is stretched to make it 0.1% longer, the percentage change in its resistance is

a)		0.1%
b)		0.3%
c)		2%
d)		0.2%

41. In a meter bridge, with a standard resistance of 5 $Ω$ in the left gap, the ratio of balancing lengths on the meter bridge wire is 2:3. The unknown resistance is

a)		1 $Ω$
b)		15 $Ω$
c)		10 $Ω$
d)		7.5 $Ω$

42. The electrical resistivity of a sample

a)		is proportional to its length
b)		is proportional to the area if cross section
c)		is inversely proportional to its length
d)		neither depends on the length nor on the area of cross section

43. A potentiometer is a device for

a)		measuring potential energy
b)		measuring current
c)		measuring electrical power
d)		comparing emfs of two sources

44. A galvanometer can be converted to a voltameter by connecting

a)		a low resistance in series
b)		a low resistance in parallel
c)		a high resistance in series
d)		a high resistance in parallel

45. In a moving coil galvanometer the deflector of the coil $θ$ is related to the electric current by the relation

a)		1 $α$ tan $θ$
b)		1 $α$ $θ^{2}$
c)		1 $α θ$
d)		1 $α \sqrt{θ}$

46. A moving coil galvanometer of resistance 50 $Ω$ gives a full scale deflection when a current of 0.5 mA is passed through it. The resistance required to convert it into a voltameter of range 10 volt is

a)		1995 $Ω$
b)		2000 $Ω$
c)		20000 $Ω$
d)		19950 $Ω$

47. The current flowing through a galvanometer of resitance 500 ohms is to be reduced by 80%, what is the value of shunt resistance to be connected? Assume that total current remains constant

a)		125 ohm
b)		12.5 ohm
c)		500 ohm
d)		50 ohm

48. An horizontal wire carries a current east to west. The direction of magnetic field set up by the current at a point directly above the wire is towards

a)		north
b)		south
c)		east
d)		west

49. An alpha particle and a beta particle are moving with equal velocities perpendicular to the direction of uniform magnetic field the magnitude of forces due to the field acting on each of them

a)		are the same
b)		differ by a factor of 2
c)		differ by a factor of 4
d)		differ by a factor of 6

50. An electron of charge $1.6 \times 10^{- 19} C$ and mass $1.0 \times 10^{- 30}$ kg moves in a circular orbit with a speed of $5.0 \times 10^{6}$ m/s, under the influence of a magnetic flux density $2.0 \times 10^{- 2} T$ . What forces does it experience?

a)		$1.66 \times 10^{- 44} N$
b)		$1.66 \times 10^{- 14} N$
c)		$3.2 \times 10^{- 24} J$
d)		$6.4 \times 10^{- 28} N$