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NCERT Solutions for class 12 Physics | Chapter 3 - Current Electricity

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Free download in PDF Class 12 Physics Chapter 3 Current Electricity Multiple Choice Questions and Answers for Board, JEE, NEET, AIIMS, JIPMER, IIT-JEE, AIEE and other competitive exams. MCQ Questions for Class 12 Physics with Answers were prepared based on the latest exam pattern. These short solved questions or quizzes are provided by Gkseries. These will help the students for preparation of their examination./p>

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(1) Two conductors of equal length and radii the ratio of 2 : 3 are; connected in parallel the source of electricity. The ratio of the velocity of electrons in the conductor be :
[A] 2 : 3
[B] 4 : 9
[C] 1 : 1
[D] 3 : 2
Answer: 1 : 1
(2) The smallest resistance that can be obtained by the combination of n resistors each resistance r is :
[A] r/n
[B] nr
[C] n/r
[D] n²r
Answer: r/n

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(3) The charge flowing in a conductor varies with time as :

Where α, β, γ are positive constants. Then the initial current (l) is given by the condition :

[A] l = α
[B] l = α²
[C] l = α-1
[D] None of these
Answer: l = α
(4) The specific resistance of a conductor increases with :
[A] increase in temperature
[B] increase in cross-sectional area
[C] decrease in length
[D] decrease in cross-sectional area
Answer: increase in temperature
(5) How many joules are equal to I kWh ?
[A] 3.6 × 104
[B] 3.6 × 105
[C] 3.6 × 106
[D] None of these
Answer: 3.6 × 106
(6) The emf of a car battery is about:
[A] 2.5 V
[B] 4.5 V
[C] 8.6 V
[D] 12 V
Answer: 12 V
(7) Why is the Wheatstone bridge more accurate than other methods of measuring resistances: ‘
[A] It is a null method
[B] It is based on Kirchhoffs laws
[C] It has four resistances
[D] It does not involve ohm’s law
Answer: It is a null method
(8) When three identical bulbs of 60 W, 200 V rating are connected in series to a 200 V supply, the power drawn by them will be:
[A] 20 W
[B] 60 W
[C] 180 W
[D] 10 W
Answer: 20 W
(9) Kirchhoffs first and second laws for electrical circuits are consequences of:
[A] conservation of energy
[B] conservation of electrical charge and energy respectively
[C] conservation of electric charge
[D] neither conservation of energy nor electric charge
Answer: conservation of electrical charge and energy respectively
(10) How much electric energy is consumed by a 100 W lamp used for 6 hours everyday for 30 days?
[A] 18 kJ
[B] 18 kWh
[C] 1.8 J
[D] None of these
Answer: 18 kWh
(11) Two wires of copper are of the same length but’have different diameters. When they are connected in series across a battery, the heat generated is H1 When connected in parallel across the same battery, the heat generated during the same time is H2 Then :
[A] H1 = H2
[B] H1 < H2
[C] H1 > H2
[D] H1 > H2
Answer: H1 < H2
(12) Siemen is the unit of:
[A] resistance
[B] conductance
[C] specific conductance
[D] None of these
Answer: conductance
(13) The length of a conductor is halved. Its resistance will be :
[A] halved
[B] doubled
[C] unchanged
[D] quadrupled
Answer: halved
(14) The specific resistance of a rod of copper as compared to that of thin wire of copper is :
[A] less
[B] more
[C] same
[D] depends upon the length and area of cross-section of the wire
Answer: same
(15) Given three equal resistors, how many different combinations (taken all of them together) can be made?
[A] 3
[B] 4
[C] 5
[D] 6
Answer: 4
(16) The resistance of a human body is about:
[A] 12 Ω
[B] 120 Ω
[C] 12 KΩ
[D] 120 MΩ
Answer: 12 KΩ
(17) Specific resistance of ali metals is mostly affected by:
[A] temperature
[B] pressure
[C] magnetic field
[D] volume
Answer: temperature
(18) In the above question, the conductance:
[A] halved
[B] doubled
[C] unchanged
[D] quadrupled
Answer: doubled
(19) Suppose H1 is the heat generated per second in the filament of a 100 W, 250 V lamp and H2 is the heat generated in the filament of a 200 W, 250 V lamp. Then H1/H2 is equal to:
[A] 1
[B] 2
[C] 1/2
[D] 1/4
Answer: 1/2
(20) A 5 A fuse wire can with stand a maximum power of 1 W in circuit. The resistance of the fuse wire is:
[A] 0.2 Ω
[B] 5 Ω
[C] 0.4 Ω
[D] 0.04 Ω
Answer: 0.04 Ω

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