# current electricity neet questions with solutions pdf

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*current electricity neet questions with solutions pdf. It also contains pdf for neet questions of class 12 physics chapter 3 current electricity*

*jee questions, aiims important questions at one place to get you all prepared for your neet, aiims ,jee main, advance exams as well as cbse board exams and other board exams. Visit my nawendu classes youtube channel for more help.*

1. Three resistances each of 4 Ω are connected to form a triangle. The resistance between any two terminals is

CBSE AIPMT 1993

Answer- $\frac{8}{3}\Omega $

2. In the network shown in figure each resistance is 1Ω. The effective resistance between A and B is

CBSE AIPMT 1990

Answer-$\frac{8}{7}\Omega $

3. What will be the equivalent resistance of circuit shown in figure between two points A and D ?

CBSE AIPMT 1996

Answer- 30 Ω

4. . n equal resistors are first connected in series and then connected in parallel. What is the ratio of the maximum to the minimum resistance?

CBSE AIPMT 1989

Answer- ${{n}^{2}}$

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

CBSE AIPMT 1988

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

CBSE AIPMT 1988

Answer- 125:15:1

6. You are given several identical resistances each of value R = 10 Ω and each capable of carrying a maximum current of 1A. It is required to make a suitable combination of these resistances of 5 Ω which can carry a current of 4 A. The minimum number of resistances of the type R that will be required for this job is

CBSE AIPMT 1990

6. You are given several identical resistances each of value R = 10 Ω and each capable of carrying a maximum current of 1A. It is required to make a suitable combination of these resistances of 5 Ω which can carry a current of 4 A. The minimum number of resistances of the type R that will be required for this job is

CBSE AIPMT 1990

Answer- 8

7. n resistance each of r ohm, when connected in parallel given an equivalent resistance of R ohm. If these resistances were connected in series, the combination would have resistance in ohms, equal to

CBSE AIPMT 2004

7. n resistance each of r ohm, when connected in parallel given an equivalent resistance of R ohm. If these resistances were connected in series, the combination would have resistance in ohms, equal to

CBSE AIPMT 2004

Answer- ${{n}^{2}}R$

8. Two wires of the same metal have same length, but their cross-sections are in the ratio 3:1. They are joined in series. The resistance of thicker wire is 10 Ω. The total resistance of the combination will be

CBSE AIPMT 1995

8. Two wires of the same metal have same length, but their cross-sections are in the ratio 3:1. They are joined in series. The resistance of thicker wire is 10 Ω. The total resistance of the combination will be

CBSE AIPMT 1995

Answer- 40 Ω

9. Seven resistances are connected as shown in the given figure . The equivalent resistance between A and B is

AIIMS 2009

Answer- 4 ohm

10. All resistances in the diagram are in ohm . Find the effective resistance between the points A and B .

9. Seven resistances are connected as shown in the given figure . The equivalent resistance between A and B is

AIIMS 2009

Answer- 4 ohm

10. All resistances in the diagram are in ohm . Find the effective resistance between the points A and B .

IIT 1980

Answer- 2 ohm

11. The equivalent resistance between points A and B of the circuit given below is

IIT 1987

Answer- R/2

12. If a negligibly small current is passed through a wire of length 15 m and of resistance 5 Ω having uniform cross-section of $6\times {{10}^{-7}}{{m}^{2}}$ , then coefficient of resistivity of material, is

CBSE AIPMT 1996

CBSE AIPMT 1996

Answer- $2\times {{10}^{-7}}\Omega m$

13. Resistivity of potentiometer wire is ${{10}^{-7}}\Omega m$ and its area of cross-section is ${{10}^{-6}}{{m}^{2}}$ . When a current i = 0.1 A flows through the wire , its potential gradient is

CBSE AIPMT 2001

Answer- ${{10}^{-2}}v/m$

14. When a wire uniform cross-section $\alpha $ , length l and resistance R is bent into a complete circle , resistance between two of diametrically opposite points will be

CBSE AIPMT 2005

Answer- R / 4

15. A wire of resistance 12 $\Omega {{m}^{-1}}$ is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite points A and B as shown in the figure is

CBSE AIPMT 2009

CBSE AIPMT 2001

Answer- ${{10}^{-2}}v/m$

14. When a wire uniform cross-section $\alpha $ , length l and resistance R is bent into a complete circle , resistance between two of diametrically opposite points will be

CBSE AIPMT 2005

Answer- R / 4

15. A wire of resistance 12 $\Omega {{m}^{-1}}$ is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite points A and B as shown in the figure is

CBSE AIPMT 2009

Answer- $0.6\pi \Omega $

16. Same length of two identical wires are first connected is series and then in parallel , then the amount of heat produced in both the conditions are in ratio

AIIMS 2000

Answer- 4:1

17. The value of current I in the circuit as shown in figure , is

AIIMS 1998

Answer- 0.8 A

18. A wire of length L is drawn such that its diameter is reduced to half of its original diameter . if the initial resistance of wire were 10 ohm, its new resistance would be

AIIMS 2003

Answer- 160 Ohm

19. If a wire of resistance R is melted and re-casted to half of its length, then the new resistance of the wire will be

CBSE AIPMT 1995

Answer- R/4

20. A wire of a certain material is stretched slowly by 10 percent. Its new resistance and specific resistance become respectively

CBSE AIPMT 2008

Answer- 1.2 times, same

21. A wire of resistance 4 Ω is stretched to twice its original length. The resistance of stretched wire would be

NEET 2013

Answer- 16 Ω

22. The resistance of a wire is R ohm. If it is melted and stretched to n times its original length, its new resistance will be

NEET 2017

Answer- \[{{n}^{2}}R\]

23. Determine the current drawn from a 12V supply with internal resistance 0.5 ohm by the infinite network shown in Figure. Each resistor has 1Ω resistance.

20. A wire of a certain material is stretched slowly by 10 percent. Its new resistance and specific resistance become respectively

CBSE AIPMT 2008

Answer- 1.2 times, same

21. A wire of resistance 4 Ω is stretched to twice its original length. The resistance of stretched wire would be

NEET 2013

Answer- 16 Ω

22. The resistance of a wire is R ohm. If it is melted and stretched to n times its original length, its new resistance will be

NEET 2017

Answer- \[{{n}^{2}}R\]

23. Determine the current drawn from a 12V supply with internal resistance 0.5 ohm by the infinite network shown in Figure. Each resistor has 1Ω resistance.

Answer- $1+\sqrt{3}\Omega $ , 3.7 A

24. Two metal wires of identical dimensions are connected in series. The if ${{\sigma }_{1}}$ and ${{\sigma }_{2}}$ are the conductivities of the metal wires respectively, the effective conductivity of the combination is

CBSE AIPMT 2015

Answer- $\frac{2{{\sigma }_{1}}{{\sigma }_{2}}}{{{\sigma }_{1}}+{{\sigma }_{2}}}$

25. If the resistance of a conductor is 5 Ω at 50°C and 7 Ω at 100°C, then the mean temperature coefficient of resistance (of the material) is

CBSE AIPMT 1996

Answer- 0.01 / ⁰C

26. A silver wire has a resistance of 1.6 ohm at 25.5 degree and a resistance of 2.5 ohm at 100 degree , then temperature coefficient of resistance of silver is

J & K CET

Answer- $7.55\times {{10}^{-3}}{}^\circ {{C}^{-1}}$

27. In the circuit of figure, the current in 4Ω resistance is 1.2 A, what is the potential difference between B and C?

CBSE AIPMT 1994

Answer- 3.6 V

28. Current through 3 Ω resistor is 0.8 A, then potential drop through 4 Ω resistor is

CBSE AIPMT 1993

29. Two batteries of emf 4 V and 8 V with internal resistance 1Ω and 2 Ω are connected in a circuit with a resistance of 9Ω as shown in figure. The current and potential difference between the points P and Q are

CBSE AIPMT 1988

Answer- 1/3 A and 3 V

30. A 6 V battery is connected to the terminals of a 3 m long wire of uniform thickness and resistance of 100 $\Omega $ . The difference of potential between two points on the wire separated by a distance of 50 cm will be

CBSE AIPMT 2004

Answer- 1 V

31. The potential difference (${{V}_{A}}-{{V}_{B}}$) between the points A and B in the given figure is

NEET 2016

Answer- +9 V

32. Five equal resistances each of resistance R are connected as shown in the figure. A battery of 4 V volts is connected between A and B. The current flowing in AFCEB will be

CBSE AIPMT 2004

Answer- V / 2R

33. A cell has an emf 1.5 V. When connected across an external resistance of the 2 Ω , the terminal potential difference falls to 1.0 V. The internal resistance of the cell is

CBSE AIPMT 2000

Answer- 1.0 Ω

34. For a cell, the terminal potential difference is 2.2 V when circuit is open and reduces to 1.8 V when cell is connected to a resistance R = 5Ω , the internal resistance ( r ) of cell is

CBSE AIPMT 2002

Answer- $\frac{10}{9}\Omega $

35. A current of 2 A flows through a 2 Ω resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9Ω resistor. The internal resistance of the battery is

CBSE AIPMT 2011

Answer- 1 / 3 Ω

36. The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is

NEET 2013

Answer- 0.5 Ω

37. A battery is charged at a potential of 15 V for 8 h when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 h , The mean terminal voltages during discharge is 14 V. The watt- hour efficiency of the battery is

CBSE AIPMT 2004

Answer- 87.5%

38. Two bulbs 25W ,220V and 100W , 220V are given which has higher resistance ?

CBSE AIPMT 2000

Answer- 25 W bulb

39. An electric bulb marked 40W and 200V , is used in a circuit of supply voltage 100V Now, its power is

AIIMS 2002

Answer- 10W

40. An electric bulb marked as 50 W-200 V is connected across a 100 V supply. The present power of the bulb is

WB JEE

Answer- 12.5 W

41. A 100 W 200V bulb is connected to a 160 V power supply. The power consumption would be

CBSE AIPMT 1997

Answer- 64W

42. Two 220V , 100W bulbs are connected in first series and them in parallel. Each time of combination is connected to a 220 V AC supply line. The power drown by the combination in each case respectively will be

CBSE AIPMT 2003

Answer- 50W, 200W

43. In India, electricity is supplied for domestic use at 220 V. It is supplied at 110V in USA . If the resistance of a 60 watt bulb for use in India is R is the resistance of a 60 W bulb for use in USA will be

CBSE AIPMT 2004

Answer- $\frac{R}{4}$

44. When three identical bulbs of 60 watt ,200V rating are connected in series to a 200 V supply , the power drown by them will be

CBSE AIPMT 2004

Answer- 20W

45. Two electric bulbs rated 50W and 100V are glowing at full power, when used in parallel with a battery of emf 120V and internal resistance 10 ohm. The maximum number of bulbs that can be connected in the circuit when glowing is full power, is

AIIMS 2008

Answer- 4

46. If two bulbs of wattages 25 W and 100W respectively each rated by 220 V are connected in series with the supply of 440 V ,which bulb will fuse?

AIIMS 2010

Answer- 25 W bulb

47. A current of 2A passing through a conductor produces 80 J of heat in 10s. The resistance of the conductor in ohm is

CBSE AIPMT 1989

Answer- 2

48. Three equal resistors connected In series across a source of emf together dissipated 10W of power. What will be power dissipated in watt if the same resistors are connected in parallel across the same source of emf ?

CBSE AIPMT 1998

Answer- 90

49. A heating coil is labelled 100W ,220V . The coil is cut in two equal halves and the two piece are joined in parallel to the same source . The energy liberated per second unit

CBSE AIPMT 1995

Answer- 400 J

50. A $4\mu F$ Conductor is charged to 400V and then its plate are joined through a resistance of 1 kilo ohm . The heat produced in the resistance is

CBSE AIPMT 1994

Answer- 0.32 J

51. An electric kettle has two heating coils. When one of the coil is connected to an AC source , the water in the kettle boils in 10 min. When the other coils is used the water boils in 40min . if both the coils are connected in parallel the time taken by the same quantity of water to boil will be

CBSE AIPMT 2003

Answer- 8min

52. A ${{5}^{\circ }}C$ rise in temperature is observed in a conductor by passing a current. When the current is doubled the rise in temperature will be approximately

CBSE AIPMT 1998

Answer- ${{20}^{\circ }}C$

53. A 5A fuse wire can withstand and maximum power of 1W in a circuit . the resistance of the fuse wire is

CBSE AIPMT 2005

Answer- 0.04 ohm

54. Power dissipated across the 8 ohm resistor in the circuit shown here is 2 W . The power dissipated in watt units across the 3 ohm resistor is

CBSE AIMPT 2006

Answer- 3.0

55. The total power dissipated in watts in the circuit shown here is

CBSE AIPMT 2007

Answer- 54

56. A current of 5 A passes through a copper conductor ( resistivity = \[1.7\times {{10}^{-8}}\Omega m\] ) of radius of cross-section 5 mm. Find the mobility of the charges, if their drift velocity is $1.1\times {{10}^{-3}}$ m/s.

IIT 2019 Main ,10 April II

Answer- $1.0{{m}^{2}}/Vs$

57. The equivalent resistance between P and Q in the figure is approximately.

Answer- 5 ohm

58. When 5V potential difference is applied across a wire of length 0. 1 m, the drift speed of electrons is $25\times {{10}^{-4}}m{{s}^{-1}}$. If the electron density in the wire is $8\times {{10}^{28}}{{m}^{-3}}$ the resistivity of the material is close to

IIT 2015 Main

Answer- $1.6\times {{10}^{-5}}\Omega m$

59. If power dissipated in the 9 ohm resistor in the circuit shown is 36 W, the potential difference across the 2 ohm resistor is

CBSE AIPMT 2011

Answer - 10 V

60. An electric kettle takes 4 A current at 220 V. How much time will take to boil 1 Kg of water from temperature 20 degree centigrade ?

CBSE AIPMT 2008

Answer- 6.3 minute

61. A current of 3 A flows through the 2 ohm resistor shown in the circuit. The power dissipated in the 5 ohm resistor is

CBSE AIPMT 2008

Answer- 5W

62. The current (i) in the given circuit is

CBSE AIPMT 1999

Answer- 2 A

63. Three resistance P , Q , R each of 2 Ω and an unknown resistance S from the four arms of a Wheatstone bridge circuit. When a resistance of 6 Ω is connected in parallel to S the bridge gets balanced. What is the value of S ?

CBSE AIPMT 2007

Answer- 3 Ω

64. In a Wheatstone bridge resistance of each of the four sides is 10 Ω . If the resistance of the galvanometer is also 10 Ω then effective resistance of the bridge will be

CBSE AIPMT 2001

Answer- 10 Ω

65. A bridge circuit is shown in figure. The equivalent resistance between A and B will be

CBSE AIPMT 2000

Answer- $\frac{14}{3}\Omega $

66. A potentiometer consists of a wire of length 4 m and resistance 10 Ω. It is connected to a cell of emf 2 V. The potential gradient of wire is

CBSE AIPMT 1999

Answer- 0.5 V / m

67. In a Wheatstone bridge, all the four arms have equal resistance R. If the resistance of the galvanometer arm is also R, the equivalent resistance of the combination as seen by the battery is

CBSE AIPMT 2003

Answer- R

68. Determine the current in each branch of the network shown in Figure.

Answer- Current in branch AB = (4/17) A,

in BC = (6/17) A, in CD = (–4/17) A,

in AD = (6/17) A,

in BD. = (–2/17) A,

total current = (10/17) A

69. A cell can be balanced against 110 cm and 100 cm of potentiometer wire, respectively with and without being short circuited through a resistance of 10 Ω. Its internal resistance is

CBSE AIPMT 2008

Answer- 1.0 Ω

70. In meter bridge , the balancing length from left is found to be 20 cm when standard resistance of 1 Ω is in right gap. The value of unknown resistance is

CBSE AIPMT 1999

Answer- 0.25 Ω

71. The mean free path of electrons in a metal is 4 x 10-8 m. The electric field which can give on an average 2 eV energy to an electron in the metal will be in unit of Vm-1

CBSE AIPMT 2009

Answer- $5\times {{10}^{7}}$

72. See the electrical circuit shown in this figure. Which of the following equations is a correct equation for it?

58. When 5V potential difference is applied across a wire of length 0. 1 m, the drift speed of electrons is $25\times {{10}^{-4}}m{{s}^{-1}}$. If the electron density in the wire is $8\times {{10}^{28}}{{m}^{-3}}$ the resistivity of the material is close to

IIT 2015 Main

Answer- $1.6\times {{10}^{-5}}\Omega m$

59. If power dissipated in the 9 ohm resistor in the circuit shown is 36 W, the potential difference across the 2 ohm resistor is

CBSE AIPMT 2011

Answer - 10 V

60. An electric kettle takes 4 A current at 220 V. How much time will take to boil 1 Kg of water from temperature 20 degree centigrade ?

CBSE AIPMT 2008

Answer- 6.3 minute

61. A current of 3 A flows through the 2 ohm resistor shown in the circuit. The power dissipated in the 5 ohm resistor is

CBSE AIPMT 2008

Answer- 5W

62. The current (i) in the given circuit is

CBSE AIPMT 1999

Answer- 2 A

63. Three resistance P , Q , R each of 2 Ω and an unknown resistance S from the four arms of a Wheatstone bridge circuit. When a resistance of 6 Ω is connected in parallel to S the bridge gets balanced. What is the value of S ?

CBSE AIPMT 2007

Answer- 3 Ω

64. In a Wheatstone bridge resistance of each of the four sides is 10 Ω . If the resistance of the galvanometer is also 10 Ω then effective resistance of the bridge will be

CBSE AIPMT 2001

Answer- 10 Ω

65. A bridge circuit is shown in figure. The equivalent resistance between A and B will be

CBSE AIPMT 2000

Answer- $\frac{14}{3}\Omega $

66. A potentiometer consists of a wire of length 4 m and resistance 10 Ω. It is connected to a cell of emf 2 V. The potential gradient of wire is

CBSE AIPMT 1999

Answer- 0.5 V / m

67. In a Wheatstone bridge, all the four arms have equal resistance R. If the resistance of the galvanometer arm is also R, the equivalent resistance of the combination as seen by the battery is

CBSE AIPMT 2003

Answer- R

68. Determine the current in each branch of the network shown in Figure.

Answer- Current in branch AB = (4/17) A,

in BC = (6/17) A, in CD = (–4/17) A,

in AD = (6/17) A,

in BD. = (–2/17) A,

total current = (10/17) A

69. A cell can be balanced against 110 cm and 100 cm of potentiometer wire, respectively with and without being short circuited through a resistance of 10 Ω. Its internal resistance is

CBSE AIPMT 2008

Answer- 1.0 Ω

70. In meter bridge , the balancing length from left is found to be 20 cm when standard resistance of 1 Ω is in right gap. The value of unknown resistance is

CBSE AIPMT 1999

Answer- 0.25 Ω

71. The mean free path of electrons in a metal is 4 x 10-8 m. The electric field which can give on an average 2 eV energy to an electron in the metal will be in unit of Vm-1

CBSE AIPMT 2009

Answer- $5\times {{10}^{7}}$

72. See the electrical circuit shown in this figure. Which of the following equations is a correct equation for it?

CBSE AIPMT 2009

Answer- ${{\varepsilon }_{1}}-\left( {{i}_{1}}+{{i}_{2}} \right)R-{{i}_{1}}{{r}_{1}}=0$

73. If voltage across a bulb rated 220 V-100 W drops by 2.5% of its rated value, the percentage of its rated value by which the power would decrease is

CBSE AIPMT 2012

Answer- 5%

74. In the circuit shown, the cells A and B have negligible resistances. For ${{V}_{A}}=12V$ , ${{R}_{1}}=500\Omega $ and R= 100 Ω the galvanometer (G) shows no deflection, The value of VB is

CBSE AIPMT 2012

Answer- 2 V

75. The resistances in the two arms of the meter bridge are 5Ω and RΩ , respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6 ${{l}_{1}}$. The resistance R, is

CBSE AIPMT 2014

Answer- 15Ω

76. A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance R, connected across the given cell, has values of (i) infinity, (ii) 9.5 Ω the balancing lengths, on the potentiometer wire are found to be 3 m and 2.85 m, respectively. The value of internal resistance of the cell is

CBSE AIPMT 2014

Answer- 0.5Ω

77. Two cites are 150 Km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 V and the average resistance per km is 0.5 ohm. The power loss in the wire is

CBSE AIPMT 2014

Answer- 19.2 kw

78. A potentiometer wire has length 4 m and resistance 8 Ω. The resistance that must be connected in series with the wire and an accumulator of emf 2V , so as to get a potential gradient 1 mV per cm on the wire is

CBSE AIPMT 2015

Answer- 32 Ω

79. A potentiometer wire of length L and a resistance r are connected in series with a battery of e.m.f. ${{E}_{0}}$ , and a resistance ${{r}_{1}}$ . An unknown e.m.f. is balanced at a length l of the potentiometer wire. The e.m.f. E will be given by

CBSE AIPMT 2015

Answer- $\frac{{{E}_{0}}r}{(r+{{r}_{1}})}\cdot \frac{l}{L}$

80. A potentiometer wire is 100 cm long and a constant potential difference is maintained across it . Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf is

NEET 2016

Answer- 3 : 2

81. The resistances of the four arms P,Q,R and S in a Wheatstone bridge are 10 Ω, 30 Ω , 30 Ω and 90 Ω respectively. The emf and internal resistance of the cell are 7 V and 5Ω respectively. If the galvanometer resistance is 50 Ω, the current drawn from the cell will be

NEET 2013

Answer- 0.2 A

82. In the figure shown , the capacity of the condenser C is 2$\mu F$ . The current in 2 ohm resistor is

AIIMS 2007

Answer- 0.9A

83. The voltage of clouds is $4\times {{10}^{6}}$ V with respect to ground. In a lighting strike lasting 100 ms, a charge of 4C is delivered to the ground . The power of lighting strike is

AIIMS 2006

Answer- 160MW

84. 6 ohm and 12 ohm resistors are connected in parallel. This combination is connected in series with a 10 V battery and 6 ohm resistor. What is the potential difference between the terminals of the 12 ohm resistor?

AIIMS 2012

Answer- 4 V

85. Charge passing through a conductor of cross-section area A = 0.3 \[{{m}^{2}}\] is given by q =3${{t}^{2}}$ + 5t + 2 in coulomb, where t is in second. What is the value of drift velocity at t = 2 s ? (Given, $n=2\times {{10}^{25}}/{{m}^{3}}$ )

AIIMS 2012

Answer- $1.77\times {{10}^{-5}}m/s$

86. A capacitor of capacitance 5 $\mu F$ is connected as shown in the figure. The internal resistance of the cell is 0.5 ohm. The amount of charge on the capacitor plate is

AIIMS 2011

Answer- $10\mu C$

87. There are N cells in the circuit of figure. The emf and internal resistance of each cell is E and r respectively. The points A and B in the circuit divide the circuit into n and N – n cells. The current in the circuit is

AIIMS 2013

Answer- E / r

88. Consider the diagram shown below.

A voltmeter of resistance 150 ohm is connected across A and B . The potential drop across B and C measured by voltmeter is

AIIMS 2015

Answer- 31 V

89. In the arrangement shown in figure, the current through 5 ohm resistor is

AIIMS 2015

Answer- 2A

90. The charge following through a resistance R varies with time t as $Q=at-b{{t}^{2}}$ ,where a and b are positive constants. The total heat produced in R is

NEET 2016

Answer - $\frac{{{a}^{3}}R}{6b}$

91. A filament bulb [500 W, 100 V] is to be used in a 230 V main supply, When a resistance R is connected in series ,it works perfectly and the bulb consumes 500 W. The value of R is

NEET 2016

90. The charge following through a resistance R varies with time t as $Q=at-b{{t}^{2}}$ ,where a and b are positive constants. The total heat produced in R is

NEET 2016

Answer - $\frac{{{a}^{3}}R}{6b}$

91. A filament bulb [500 W, 100 V] is to be used in a 230 V main supply, When a resistance R is connected in series ,it works perfectly and the bulb consumes 500 W. The value of R is

NEET 2016

Answer- 26 ohm

92. The n rows each containing m cells in series are joined in parallel. Maximum current is taken from this combination across an external resistance of 3 ohm. lf the total number of cells used is 24 and internal resistance of each cell is 0.5 ohm, then

AIIMS 2016

Answer- m = 12, n = 2

93. A cylindrical conductor AB of non-uniform area of cross-section carries a current of 5A. the radius of the conductor at one end A is 0.5 cm. the current density at the other end of the conductor is half of the value at A. The radius of the conductor at the end B is nearly

AIIMS 2017

Answer- 0.7 cm

94. Two batteries, one of emf 18V and internal resistance 2 ohm and the other of emf 12V and internal resistance 1 ohm are connected as shown. The voltmeter V will record a reading of

AIIMS 2017, CBSE AIPMT 2005

Answer- 14V

95. In the following diagram, the current through 2 ohm resistor is

AIIMS 2018

Answer- 9/2 A

96. A 25 W and a 100W bulbs are joined in series and connected to the mains . Which bulb will glow brighter ?

IIT 1979

Answer- 25 w

97. In a potentiometer experiment, it is that no current passes through the galvanometer when the terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a resistance of 5 ohm, a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.

IIT 2018 Main

Answer- 1.5 ohm

98. A resistance is shown in the figure Its value and tolerance are given respectively by,

IIT 2019 Main ,9 April I

Answer- 27 k ohm,10%

99. A uniform metallic wire has a resistance of 18 ohm and is bent into an equilateral triangle .Then, the resistance between any two vertices of the triangle is

IIT 2019 Main ,10 jan I

Answer- 4 ohm

100. A copper wire is stretched to make it 0.5% longer. The percentage change in its electrical resistance , If the volume remains unchanged is

IIT 2019 Main ,9 jan I

Answer- 1.0 %

101. Figure shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 ohm maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V (for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 kilo ohm is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf E and the balance point found similarly, turns out to be at 82.3 cm length of the wire.

(a) What is the value E?

(b) What purpose does the high resistance of 600 kilo ohm have?

(c) Is the balance point affected by this high resistance?

(d) Would the method work in the above situation if the driver cell of the potentiometer had an emf of 1.0V instead of 2.0V?

(e) Would the circuit work well for determining an extremely small emf, say of the order of a few mV (such as the typical emf of a thermo-couple)? If not, how will you modify the circuit?

Answer- (a) E = 1.25 V.

(b) To reduce current through the galvanometer when the movable contact is far from the balance point. (c) No.

(d) No. If E is greater than the emf of the driver cell of the potentiometer, there will be no balance point on the wire AB.

(e) The circuit, as it is, would be unsuitable, because the balance point (for ε of the order of a few mV) will be very close to the end A and the percentage error in measurement will be very large. The circuit is modified by putting a suitable resistor R in series with the wire AB so that potential drop across AB is only slightly greater than the emf to be measured. Then, the balance point will be at larger length of the wire and the percentage error will be much smaller.

92. The n rows each containing m cells in series are joined in parallel. Maximum current is taken from this combination across an external resistance of 3 ohm. lf the total number of cells used is 24 and internal resistance of each cell is 0.5 ohm, then

AIIMS 2016

Answer- m = 12, n = 2

93. A cylindrical conductor AB of non-uniform area of cross-section carries a current of 5A. the radius of the conductor at one end A is 0.5 cm. the current density at the other end of the conductor is half of the value at A. The radius of the conductor at the end B is nearly

AIIMS 2017

Answer- 0.7 cm

94. Two batteries, one of emf 18V and internal resistance 2 ohm and the other of emf 12V and internal resistance 1 ohm are connected as shown. The voltmeter V will record a reading of

AIIMS 2017, CBSE AIPMT 2005

Answer- 14V

95. In the following diagram, the current through 2 ohm resistor is

AIIMS 2018

Answer- 9/2 A

96. A 25 W and a 100W bulbs are joined in series and connected to the mains . Which bulb will glow brighter ?

IIT 1979

Answer- 25 w

97. In a potentiometer experiment, it is that no current passes through the galvanometer when the terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a resistance of 5 ohm, a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.

IIT 2018 Main

Answer- 1.5 ohm

98. A resistance is shown in the figure Its value and tolerance are given respectively by,

IIT 2019 Main ,9 April I

Answer- 27 k ohm,10%

99. A uniform metallic wire has a resistance of 18 ohm and is bent into an equilateral triangle .Then, the resistance between any two vertices of the triangle is

IIT 2019 Main ,10 jan I

Answer- 4 ohm

100. A copper wire is stretched to make it 0.5% longer. The percentage change in its electrical resistance , If the volume remains unchanged is

IIT 2019 Main ,9 jan I

Answer- 1.0 %

101. Figure shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 ohm maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V (for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 kilo ohm is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf E and the balance point found similarly, turns out to be at 82.3 cm length of the wire.

(a) What is the value E?

(b) What purpose does the high resistance of 600 kilo ohm have?

(c) Is the balance point affected by this high resistance?

(d) Would the method work in the above situation if the driver cell of the potentiometer had an emf of 1.0V instead of 2.0V?

(e) Would the circuit work well for determining an extremely small emf, say of the order of a few mV (such as the typical emf of a thermo-couple)? If not, how will you modify the circuit?

Answer- (a) E = 1.25 V.

(b) To reduce current through the galvanometer when the movable contact is far from the balance point. (c) No.

(d) No. If E is greater than the emf of the driver cell of the potentiometer, there will be no balance point on the wire AB.

(e) The circuit, as it is, would be unsuitable, because the balance point (for ε of the order of a few mV) will be very close to the end A and the percentage error in measurement will be very large. The circuit is modified by putting a suitable resistor R in series with the wire AB so that potential drop across AB is only slightly greater than the emf to be measured. Then, the balance point will be at larger length of the wire and the percentage error will be much smaller.

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