Untitled Document

Question Bank No: 1

1. Which of the following has negative temperature coefficient of resistance?

a)		Cu
b)		Al
c)		Fe
d)		Ge

2. The current in a conductor varies with time t as I =2t+3 $t^{2}$ where I is in ampere and t in seconds. Electric charge flowing through a section of the conductor during t = 2 sec to t = 3 sec is

a)		10C
b)		24C
c)		33C
d)		44C

3. How many electrons constitute current of one ampere?

a)		6.25 $\times 10^{9}$
b)		6.25 $\times 10^{18}$
c)		6.25 $\times 10^{5}$
d)		6.25 $\times 10^{6}$

4. Identify that set in which all the three substances are good conductors of electricity

a)		Cu, Ag, Ao
b)		Cu, Si, diamond
c)		Cu, Ag, plastic
d)		Cu, Ge, wood

5. A battery having emf 4V and internal resistance 0.5 $Ω$ is connected with a resistance of 4.5 $Ω,$ then the voltage at the terminals of battery is

a)		4.5V
b)		3.6V
c)		0V
d)		2V

6. The resistance will be least in a wire with dimension

a)		L/2, 2A
b)		2L, A
c)		L.A
d)		none of these

7. The resistance of a discharge tube is

a)		Ohmic
b)		non ohmic
c)		both
d)		sometime ohmic, sometimes non ohmic

8. A resistor of 0.5 $Ω$ is connected to another resistor in parallel combination to get an equivalent resistance of 0.1 $Ω .$ The resistance of second resistor is

a)		1/8 $Ω$
b)		0.2 $Ω$
c)		0.6 $Ω$
d)		8 $Ω$

9. An electron in the potentiometer wire experiences a force of 2.4 $\times 10^{- 19} N .$ The length of the potentiometer wire is 4m. The emf of the battery connected across the wire is

a)		6V
b)		4.8V
c)		4V
d)		2.4V

10. A cell of internal resistance r is connected to an external resistance R. The current will be maximum in R if.

a)		R=r
b)		R $> r$
c)		R $< r$
d)		R=r/2

11. From the fig. the potential difference across P and Q will be nearest to
currentelectricityQ12

a)		9.6V
b)		6.6V
c)		4.8V
d)		3.2V

12. To draw a maximum current from a combination of cells, How should the cells be grouped?

a)		parallel
b)		series
c)		mixed grouping
d)		depends upon the relative values of internal and external resistances

13. A wire has resistance 90 $Ω .$ It is bent in the form of an equilateral triangle. The effective resistance between two corner is

a)		30 $Ω$
b)		60 $Ω$
c)		20 $Ω$
d)		90 $Ω$

14. What is the total resistance a cross A and B in the circuit
currentelectricityQ9

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

15. You are given three equal resisters. How many resistances can be obtained by joining them in series and parallel grouping

a)		6
b)		4
c)		3
d)		2

16. According to Krichoff's law the algebric sum of the product of current and resistance as well as emf

a)		zero
b)		greater than zero
c)		less than zero
d)		to be decided by the emf

17. The V-I graph for a good conductor makes angle $40^{0}$ with V-axis. V denotes voltage I denotes current. The resistance of the conductor will be

a)		sin $40^{0}$
b)		cos $40^{0}$
c)		tan $40^{0}$
d)		cot $40^{0}$

18. Specific resistance of all metals is mostly affected by

a)		magnetic field
b)		volume
c)		pressure
d)		temperature

19. If n is the number density of free electrons in a metallic wire, then the resistance is proportional to

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

20. A wire 50cm long and 1m $m^{2}$ in cross section carries a current of 4A when connected to a 2V battery. The resistivity of the wire is

a)		2 $\times 10^{- 7} Ω m$
b)		5 $\times 10^{- 7} Ω m$
c)		4 $\times 10^{- 6} Ω m$
d)		1 $\times 10^{- 6} Ω m$

21. The amount of charge Q passed in time t through a crossection of a wire is Q= 5 $t^{2} + 3 t + 1.$ The value of current at time t =5S is

a)		9A
b)		49A
c)		53A
d)		none of the above

22. An electric kettle has two coils. When one of these is switched on, the water in the kettle boild in 6 minutes. When the other coil is switched on, the water boils in 3 minutes. If the two coils are connected in series, the time taked to boil water in the kettle, is

a)		3 minutes
b)		6 minutes
c)		2 minutes
d)		9 minutes

23. An immersion heater is rated 836 watt it should heat 1 litre of water from $20^{0} C$ to $40^{0} C$ in about

a)		200 sec
b)		100 sec
c)		836 sec
d)		418 sec

24. Three equal resistors connected in series across a source e.m.f. together dissipate 10 watt. If the same resistors are connected in parallel across the same e.m.f. the power dissipatted will be

a)		10 watt
b)		30 watt
c)		10/3 watt
d)		90 watt

25. A heater coil is cut into two parts of equal length and only one of them is used in the heater. The ratio of the heat produced by this half-coil to that by the oroginal coil is

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

26. A moving coil galvanometer of resistance of 15 $Ω$ and the meter shows full scale deflection, when a current of 0.5mA is passed through it. To convert it to a voltmeter of range 10V, the resistance required to be placed in series is

a)		10,000 $Ω$
b)		1995 $Ω$
c)		19,950 $Ω$
d)		2000 $Ω$

27. How many dry cells, each of e.m.f. 1.5 V and internal resistance 0.5 $Ω$ , must be joined in series with a resistor of 20 $Ω$ to give a current of 0.6A in the circuit?

a)		2
b)		8
c)		10
d)		12

28. A battery of e.m.f. 10 V and internal resistance 0.5 $Ω$ is connected across a variable resistance R. The value of R, for which the power delivered in it is maximum, is

a)		2 $Ω$
b)		1.5 $Ω$
c)		1 $Ω$
d)		0.5 $Ω$

29. The adjoining figure shows current in a part of an electric circuit. Then current I is
currentelectricity-q14

a)		1.7A
b)		3.7A
c)		1.3A
d)		1A

30. The resistance of a wire is R ohm. The wire is stretched 'n' times the original length. Now the resistance of the wire will be

a)		same as before
b)		nR
c)		R / n
d)		$n^{2} R$

31. We have two wires of copper one of length 100 cm and the other of 200cm. Both have equal area of cross section. The ratio of specific resistance of the wire to that of second is

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

32. A carbon resistor has a set of coaxial coloured rings in the order brown, violet, brown and silver. The value of resistance (in ohms) is

a)		(27 $\times$ 10)= $\pm 5 %$
b)		(27 $\times$ 10)= $\pm 10 %$
c)		(17 $\times$ 10)= $\pm 5 %$
d)		(17 $\times$ 10)= $\pm 10 %$

33. The current I and voltage for a given matallic wire at two different temperatures $T_{1}$ and $T_{2}$ are shown in the figure.It is concluded that
currentelectricity-q10

a)		$T_{1}$ > $T_{2}$
b)		$T_{1}$ < $T_{2}$
c)		$T_{1}$ = $T_{2}$
d)		$T_{1}$ =2 $T_{2}$

34. The temperature coefficient of resistance is positive for

a)		carbon
b)		silicon
c)		germanium
d)		aluminium

35. The electric intensity E, current density J and specific resistance k are related to each other through the relation

a)		E = j / k
b)		E=jk
c)		E= k / j
d)		k = jE

36. What is immaterial for an electric fuse?

a)		Its specific resistance
b)		Its radius
c)		Its length
d)		None of these

37. If n, e, $τ$ and m are representing electron density, charge on a electron, relaxation tine and mass of an electron respectively, then the resistance of wire length l and cross sectional area A is given by

a)		$\frac{ml}{n e^{2} τ A}$
b)		$\frac{m τ A}{n e^{2} l}$
c)		$\frac{n e^{2} τ A}{me}$
d)		$\frac{n e^{2} A}{m τ l}$

38. An ionization chamber with parallel conducting plates as anode and cathode, has $5 \times 10^{7}$ electrons and the same number of singly charged positive ions per ${cm}^{3}$ . The electrons are moving towards the anode with velocity 0.4 m/s. The current density from anode to cathode is 4 $μ$ A/ $m^{2}$ . The velocity of positive ions moving towards cathode is

a)		0.4m $s^{- 1}$
b)		zero
c)		1.6m $s^{- 1}$
d)		0.1m $s^{- 1}$

39. A current I flows through a uniform wire of diameter 'd' when the mean drift velocity is $v_{d}$ . The same current will flow through a wire of diameter d/2 made of the same material if the mean drift velocity of the electron is

a)		$v_{d}$ /4
b)		$v_{d}$ /2
c)		4 $v_{d}$
d)		2 $v_{d}$

40. A wire 50cm long and 1m $m^{2}$ in cross section carries a current of 4A when connected to a 2V battery. The resistivity of the wire is

a)		2 $\times 10^{- 7} Ω m$
b)		5 $\times 10^{- 7} Ω m$
c)		4 $\times 10^{- 6} Ω m$
d)		1 $\times 10^{- 6} Ω m$

41. A battery of emf 10V and internal resistance 0.5 $Ω$ is connected across a variable resistance R. The value of R, for which the power delivered in it, is maximum, is given by

a)		2.0 $Ω$
b)		0.25 $Ω$
c)		1.0 $Ω$
d)		0.5 $Ω$

42. A parallel combination of three resistors takes a current of 7.5A from a 30 V supply. If the two resistors are 10 $Ω$ and 12 $Ω$ , find what is the third one?

a)		4 $Ω$
b)		15 $Ω$
c)		12 $Ω$
d)		22 $Ω$

43. What is immaterial for an electric fuse wire?

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

44. Two identical heaters 220 volt, 1000 watt are placed in series with each other across 220 volt lines then the combined power is

a)		1000 watt
b)		2000 watt
c)		500 watt
d)		4000 watt

45. A 25 watt, 220 volt bulb and a 100 watt, 220 volt bulb are connected in parallel across a 440 volt lines

a)		Only 10 watt bulb will fuse
b)		Only 25 watt bulb will fuse
c)		Both bulb will fuse
d)		None of the bulb will fuse

46. The two electric bulb have tungsten filament of same length. If one of them gives 60 watts and the other 100 watt then

a)		100 watts bulb has thicker filament
b)		60 watts bulb has thicker filament
c)		Both filament are of same thickness
d)		It is not possible to get different wattage unless the length are different

47. When a current is devided between two resistors according to Kirchoff's law, then the heat produced is

a)		Zero
b)		Negligible
c)		Minimum
d)		Maximum

48. How would you arrange 48 cells each of e.m.f. 2 V and internal resistance 1.5 $Ω$ so as to send maximum current through the external resistance of 2 $Ω$ ?

a)		2 cells in 24 groups
b)		4 cells in 12 groups
c)		8 cells in 6 groups
d)		3 cells in 16 groups

49. A wire has resistance 12 ohms. It is bent in the form of a circle. The effective resistance acreoss the diameter of the circle is

a)		24 $Ω$
b)		12 $Ω$
c)		6 $Ω$
d)		3 $Ω$

50. How many combinations of three equal resistances can be made using all together?

a)		2
b)		4
c)		6
d)		9