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Objective Type Question and Answers On Class 12 Physics Chapter 3 Current Electricity

(1) A galvanometer acting as a volt meter will have with its coil.
[A] a high resistance in parallel
[B] a high resistance in series
[C] a low resistance in parallel
[D] a low resistance in series
Answer: a high resistance in series
(2) The length and radius of an electric resistance of a certain wire are doubled simultaneously, then the:
[A] resistance will be doubled and specific resistance will be halved
[B] resistance will be halved and specific resistance will remain uncharged
[C] resistance will be halved and the specific resistance will be doubled
[D] resistance and specific resistance will both remain uncharged
Answer: resistance will be halved and specific resistance will remain uncharged

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(3) Ohm’s law is valid when the temperature of conductor is :
[A] very low
[B] very high
[C] varying
[D] constant
Answer: constant
(4) n resistances, each of R Ω, are connected in parallel gives an equivalent resistance of R Ω. If these resistances were , connected in series, the combination would have a resistance in Ω is equal to
[A] n²R
[B] R/n²
[C] R/n
[D] nR
Answer: n²R
(5) Emf is measured in :
[A] joule
[B] joule/coulomb
[C] joule-coulombs
[D] joule/coulomb/metre
Answer: joule/coulomb
(6) A potential difference of 10 V is applied across a conductance of 2 S. The current in the conductor will be :
[A] 20 A
[B] 5 A
[C] 0.2 A
[D] None of these
Answer: 20 A
(7) The temperature coefficient of resistance is expressed in :
[A] °C
[B] °C-1
[C] m°C-1
[D] None of these
Answer: °C-1
(8) 1 kilowatt hour is commonly known as :
[A] unit
[B] 1 faraday
[C] 1 curie
[D] None of these
Answer: unit
(9) In an experiment with potentiometer, null point with a cell is found at 240 cm. When the cell is shunted with a resistance 2 Ω, the null point becomes 120 cm internal resistance of cell is :
[A] 4 Ω
[B] 2 Ω
[C] 1 Ω
[D] 1/2 Ω
Answer: 2/Ω
(10) The phenomenon of super-conductivity was discovered by :
[A] Ohm
[B] Onnes
[C] Edison
[D] None of these
Answer: Onnes
(11) Copper wire is used as connecting wire because :
[A] copper has high electrical resistivity
[B] copper has low electrical resistivity
[C] copper has low electrical conductivity
[D] copper has high value of elasticity
Answer: copper has low electrical resistivity
(12) A wire of resistance 3 Ω is cut into three pieces, which are then joined to form a triangle. The equivalent resistance between any corners of the triangle is :
[A] 2/3 Ω
[B] 3/2 Ω
[C] 1/2 Ω
[D] 1/3 Ω
Answer: 2/3 Ω
(13) The example of a non-ohmic resistance is:
[A] copper wire
[B] fi lament lamp
[C] carbon resistor
[D] diode
Answer: diode
(14) How many different resistances are possible with two equal resistors?
[A] 2
[B] 3
[C] 4
[D] 5
Answer: 3
(15) The speed at which tjie current travels in a conductor is nearly:
[A] 3 × 104 ms-1
[B] 3 × 106 ms-1
[C] 3 × 108 ms-1
[D] 3 × 1010 ms-1
Answer: 3 × 104 ms-1
(16) The heat sensitive device whose resistivity changes very rapidly with change of temperature is called a :
[A] resistor
[B] super-conductor
[C] thermocouple
[D] thermistor
Answer: thermistor
(17) In following figure shows currents in a part of electrical circuit, then the value of/(in ampere) is given by :

[A] 0.3 A
[B] 0.5 A
[C] 1.3 A
[D] None of these
Answer: 0.3 A
(18) An electric heating element consumes 500 W, when connected to a 100 V line. If the line voltage becomes 150 V, the power consumed Will be:
[A] 500 W
[B] 750 W
[C] 1000 W
[D] 1125 W
Answer: 750 W
(19) A uniform w ire connected across a supply produces heat H per second. If wire is cut into three equal parts and all the parts are connected in parallel across the same supply, the heat produced per second will be :
[A] H/9
[B] 9 H
[C] 3 H
[D] H/3
Answer: H/3

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