# MCQs For NCERT Class 12 Physics Chapter 3 Current Electricity

Please refer to the MCQ Questions for Class 12 Physics Chapter 3 Current Electricity with Answers. The following Current Electricity Class 12 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 12. Our experts have designed MCQ Questions for Class 12 Physics with Answers for all chapters in your NCERT Class 12 Physics book.

## Current Electricity Class 12 MCQ Questions with Answers

See below Current Electricity Class 12 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. A flow of 107 electrons per second in a conducting wire constitutes a current of
(a) 1.6 × 10–12 A
(b) 1.6 × 1026 A
(c) 1.6 × 10–26 A
(d) 1.6 × 1012 A

A

Question. 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
(a) R /n
(b) n2R
(c) R/n2
(d) nR

B

Question. Is it possible that any battery has some constant value of e.m.f but the potential difference between the plates is zero?
(a) No
(b) Yes, if another identical battery is joined in series.
(c) Yes, if another identical battery is joined in opposition in series.
(d) Yes, if another similar battery is joined in parallel.

C

Question. The temperature of the cold junction of a thermocouple is 0°C and the temperature of the hot junction is T°C. The relation for the thermo emf is given by;
E = AT-1/2BT(when A = 16 and B = 0.08). The temperature of inversion will be :
(a) 500°C
(b) 460°C
(c) 600°C
(d) 400°C

D

Question. The internal resistance of a cell is the resistance of :
(a) electrolyte used in the cell
(b) electrodes of the cell
(c) vessel of the cell
(d) none of these

A

Question. The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
(a) the resistance and the specific resistance, will both remain unchanged
(b) the resistance will be doubled and the specific resistance will be halved
(c) the resistance will be halved and the specific resistance will remain unchanged
(d) the resistance will be halved and the specific resistance will be doubled

C

Question. A given resistor has the following colour scheme of the various strips on it : Brown, black, green and silver. Its value in ohm is
(a) 1.0´104 ±10%
(b) 1.0´105 ±10%
(c) 1.0´106 ±10%
(d) 1.0´107 ±10%

C

Question. A wire of resistance 4 W is stretched to twice its original length. The resistance of stretched wire would be
(a) 8 W
(b) 16 W
(c) 2 W
(d) 4 W

B

Question. A wire of a certain material is stretched slowly by ten percent. Its new resistance and specific resistance become respectively
(a) both remain the same
(b) 1.1 times, 1.1 times
(c) 1.2 times, 1.1 times
(d) 1.21 times, same

D

Question. The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
(a) The resistance will be doubled and the specific resistance will be halved
(b) The resistance will be halved and the specific resistance will remain unchanged
(c) The resistance will be halved and the specific resistance will be doubled
(d) The resistance and the specific resistance, will both remain unchanged.

B

Question. A conductor carries a current of 50 m A. If the area of cross section of the conductor is 50 μm2, then value of the current density in Am–2 is
(a) 0.5
(b) 1
(c) 10–3
(d) 10–6

B

Question. A cell when balanced with potentiometer gave a balance length of 50 cm. 4.5 Ω external resistance is introduced in the circuit, now it is balanced on 45 cm. The internal resistance of cell is
(a) 0.25 Ω
(b) 0.5 Ω
(c) 1.0 Ω
(d) 1.5 Ω

A

Question. A 6 volt battery is connected to the terminals of a three metre long wire of uniform thickness and resistance of 100 ohm. The difference of potential between two points on the wire separated by a distance of 50 cm will be
(a) 2 volt
(b) 3 volt
(c) 1 volt
(d) 1.5 volt

C

Question. Three copper wires of lengths and cross-sectional areas are (l, A), (2l, A/2) and (l/2, 2A). Resistance is minimum in
(a) wire of cross-sectional area 2A
(b) wire of cross-sectional area A/2
(c) wire of cross-sectional area A
(d) same in all three cases.

A

Question. A wire 50 cm long and 1 mm2 in cross-section carries a current of 4 A when connected to a 2 V battery. The resistivity of the wire is
(a) 4 × 10–6 W m
(b) 1 × 10–6 W m
(c) 2 × 10–7 W m
(d) 5 × 10–7 W m

B

Question. The masses of the wires of copper is 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
(a) 1 : 3 : 5
(b) 5 : 3 : 1
(c) 1 : 25 : 125
(d) 125 : 15 : 1

D

Question. A flow of 107 electrons per second in a conducting wire constitutes a current of
(a) 1.6´10-26A
(b) 1.6´1026A
(c) 1.6´10-12A
(d) 1.6´1012A

C

Question. A 100-W bulb and a 25-W bulb are designed for the same voltage. They have filaments of the same length and material. The ratio of the diameter of the 100-W bulb to that of the 25-W bulb is
(a) 4 : 1
(b) 2 : 1
(c) √2 :1
(d) 1 : 2

B

Question. A charged particle having drift velocity of 7.5 × 10–4 m s–1 in an electric field of 3 × 10–10 V m–1, has a mobility in m2 V–1 s–1 of
(a) 2.25 × 1015
(b) 2.5 × 106
(c) 2.5 × 10–6
(d) 2.25 × 10–15

B

Question. The cell has an emf of 2V and the internal resistance of this cell is 0.1W, it is connected to a resistance of 3.9W. The voltage across the cell will be :
(a) 1.95 V
(b) 1.5 V
(c) 2 V
(d) 1.8 V

A

Question. The velocity of charge carriers of current (about 1 ampere) in a metal under normal conditions is of the order of
(a) a fraction of mm/sec
(b) velocity of light
(c) several thousand metres/second
(d) a few hundred metres per second

A

Question. The resistance of a discharge tube is
(a) non-ohmic
(b) ohmic
(c) zero
(d) both (b) and (c)

A

Question. A carbon resistor of (47 ± 4.7) kW is to be marked with rings of different colours for its identification.
The colour code sequence will be
(a) Violet – Yellow – Orange – Silver
(b) Yellow – Violet – Orange – Silver
(c) Yellow – Green – Violet – Gold
(d) Green – Orange – Violet – Gold

B

Question. Identify the set in which all the three materials are good conductors of electricity.
(a) Cu, Hg and NaCl
(b) Cu, Ge and Hg
(c) Cu, Ag and Au
(d) Cu, Si and diamond

C

Question. A capacitor of 10m F has a pot. difference of 40 volts across it. If it is discharged in 0.2 second, the average current during discharge is
(a) 2 m A
(b) 4 m A
(c) 1 m A
(d) 0.5 m A

A

Question. The amount of charge Q passed in time t through a crosssection of a wire is Q = 5 t2 + 3 t + 1. The value of current at time t = 5 s is
(a) 9 A
(b) 49 A
(c) 53 A
(d) None of these

C

Question. The resistance of a wire, used in a toaster, is found to be 75.3 Ω at room temperature (27oC) and its resistance at steady temperature 847oC is found to be 85.8 Ω. Then the temperature coefficient of this material is:
(a) 10-4 oC-1
(b) 1.70 X 10-4 oC-1
(c) 10.70 X 10-4 oC-1
(d) 100.70 X 10-4 oC-1

B

Question. In the given circuit, the LED will not glow when the value of resistor X =

(a) 726 Ω
(b) 11 Ω
(c) 121 Ω
(d) 6 Ω

D

Question. Select an incorrect statement about movement of charges, from given options:
(a) In few materials, free electrons are in influence of nuclei of neighbouring atoms such that they cannot move freely even in presence of external electric field.
(b) In solid conductors, negatively charged electrons move in the background of fixed positive ions.
(c) In electrolytic solutions, only positive ions can move.
(d) During lightning, movement of charges across clouds and earth, produces electric current of the order of ten thousand of amperes.

C

Question. The resistivity of a typical insulator (e.g.Amber) is greater than that of a metal by a factor of the order of
(a) 103
(b) 100
(c) 1022
(d) 10-3

C

Question. Two cities are 120 Km apart. Electric power is sent from one city to other city through copper wires. The fall in potential per Km is 6 V and the average resistance per Km is 1.2Ω.
The power loss in the wire is
(a) 36 W
(b) 3.6 KW
(c) 360 W
(d) 0.36 KW

B

Question. In which of the following conditions, internal resistance of a cell can be neglected ?
(a) When current drawn from the cell is small.
(b) When emf of cell is negligible.
(c) When current drawn from cell is large.
(d) When External resistor has large value.

A

Question. Which of the following R-r curves is correct? (R: Resistance, r: radius of the solid conducting wire of uniform composition)

C

Question. Potential difference between A and B in the circuit shown here is :

(a) 4 V
(b) 5.6 V
(c) 2.8 V
(d) 6 V

B

Question. Two wires of same dimensions but resistivities ⟩1 and ⟩2 are connected in series. The equivalent resistivity of the combination is:
(a) √⟩1⟩2
(b) ⟩1 + ⟩2
(c) (⟩1 + ⟩2)/2
(d) None of these

B

Question. Wires of standard resistors are made up of Constantan or Manganin because their resistivities vary ______________ with temperature.
(a) Weakly
(b) strongly
(c) moderately
(d) negligibly

Answe

A

Question. In the given diagram, the total charge transported across the conductor, to the right, in time Δt is: what are A,n V e not mentioned

(a) neAvd Δt
(b) -neAvd
(c) nevd Δt
(d) -neAvd Δt

D

Question. A potential difference of 3 V has been applied across a metal conductor of length 60 cm.
If relaxation period of electrons in this metal is 2.5 X 10-14 s, then the magnitude of drift velocity will be
(a) 2.2 X 10 -2 m/s
(b) 2.2 X 10 -4 m/s
(c) 1.1 X 10 -4 m/s
(d) 1.1 X 10 -6 m/s

A

Question. Which of the following is SI unit of temperature coefficient resistivity?
(a) (Temperature)-1
(b) (oC)-1
(c) (oF)-1
(d) (oK)-1

D

Question. The current flowing through a wire at instant t second is given as I= 3t2 + 2t + 5. The charge flowing the cross section of the wire between time 0 s and 2 s is
(a) 21 C
(b) 10 C
(c) 22 c
(d) 1 c

C

Question. During thermal motion, an electron colliding with an ion emerges with the same ____________ as before the collision’.
(a) velocity
(b) speed
(c) Acceleration
(d) Momentum

B

Question. The current density in a wire of diameter 0.2 cm carrying a current of 10 A is:
(a) 6.18 X 106 A/m2
(b) 2.18 X 106 A/m2
(c) 5.18 X 106 A/m2
(d) 3.18 X 106 A/m2

D

Question. The current at steady state through 4 Ω resistor in given circuit is: 13
(a) 9 A
(b) 0.9 A
(c) 0 A
(d) 1/0.9 A

C

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

Question. Assertion: It is advantageous to transmit electric power at high voltage.
Reason: High voltage implies high current.
(a) a
(b) b
(c) c
(d) d

B

Question. Assertion: Ohm’s law is not a fundamental law of nature.
Reason: I depends on V non-linearly at high temperature for conductors.
(a) a
(b) b
(c) c
(d) d

A

Question. The solids which have the negative temperature coefficient of resistance are
(a) metals
(b) insulators only
(c) semiconductors only
(d) insulators and semiconductors.

D

Question. Specific resistance of a conductor increases with
(a) increase in temperature
(b) increase in cross-section area
(c) increase in cross-section and decrease in length
(d) decrease in cross-section area.

A

Question. Copper and silicon is cooled from 300 K to 60 K, the specific resistance
(a) decreases in copper but increases in silicon
(b) increases in copper but decreases in silicon
(c) increases in both
(d) decreases in both.

A

Question. Which of the following acts as a circuit protection device?
(a) fuse
(b) conductor
(c) inductor
(d) switch

A

Question. An electric bulb marked 40 W and 200V, is used in a circuit of supply voltage 100V. Now its power is
(a) 10 W
(b) 20 W
(c) 40 W
(d) 100 W

A

Question. The charge flowing through a resistance R varies with time t as Q = at – bt2, where a and b are positive constants. The total heat produced in R is
(a) a Rb32
(b) a R b 3
(c) a R b 3 6
(d) a R b 3 3

C

Question. Two cities 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 volt and the average resistance per km is 0.5 W. The power loss in the wire is
(a) 19.2 W
(b) 19.2 kW
(c) 19.2 J
(d) 12.2 kW

B

Question. If voltage across a bulb rated 220 volt- 100 watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is
(a) 20%
(b) 2.5%
(c) 5%
(d) 10%

C

Question. The mean free path of electrons in a metal is 4 × 10–8 m.
The electric field which can give on an average 2 eV energy to an electron in the metal will be in units V/m
(a) 5 × 10–11
(b) 8 × 10–11
(c) 5 × 107
(d) 8 × 107

C

Question. An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20°C ? The temperature of boiling water is 100°C.
(a) 12.6 min
(b) 4.2 min
(c) 6.3 min
(d) 8.4 min

C

Question. A 5 ampere fuse wire can withstand a maximum power of 1 watt in the circuit. The resistance of the fuse wire is
(a) 0.04 ohm
(b) 0.2 ohm
(c) 5 ohm
(d) 0.4 ohm

A

Question. In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be
(a) R
(b) 2R
(c) R/4
(d) R/2

C

Question. Fuse wire is a wire of
(a) high resistance and high melting point
(b) high resistance and low melting point
(c) low resistance and low melting point
(d) low resistance and high melting point

C

Question. Two bulbs are of (40 W, 200 V), and (100 W, 200 V).
Then correct relation for their resistances is
(a) R40 < R100
(b) R40 > R100
(c) R40 = R100
(d) no relation can be predicted.

B

Question. A 5°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
(a) 20°C
(b) 16°C
(c) 10°C
(d) 12°C

A

Question. A (100 W, 200 V) bulb is connected to a 160 volts supply. The power consumption would be
(a) 100 W
(b) 125 W
(c) 64 W
(d) 80 W

C

Question. The voltage of clouds is 4 × 106 volt with respect to round. In a lighteing strike lasting 100 m sec, a charge of 4 coulombs is delivered to the ground.
The power of lightening strike is :
(a) 160 MW
(b) 80 MW
(c) 20 MW
(d) 500 KW

A

Question. One kilowatt hour is equal to
(a) 36 × 10–5 J
(b) 36 × 10–4 J
(c) 36 × 105 J
(d) 36 × 103 J

Question. A 4 mF capacitor is charged to 400 V. If its plates are joined through a resistance of 2 kW, then heat produced in the resistance is
(a) 0.64 J
(b) 1.28 J
(c) 0.16 J
(d) 0.32 J

C

Question. An electric bulb is rated 60 W, 220 V. The resistance of its filament is
(a) 870 W
(b) 780 W
(c) 708 W
(d) 807 W

D

Question. A current of 2 A, passing through a conductor produces 80 J of heat in 10 seconds. The resistance of the conductor in ohm is
(a) 0.5
(b) 2
(c) 4
(d) 20

D

Question. 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
(a) 230 W
(b) 46 W
(c) 26 W
(d) 13 W

C

Question. Two metal wires of identical dimensions are connected in series. If s1 and s2 are the conductivities of the metal wires respectively, the effective conductivity of the combination is
(a) σ1+σ2/σ1σ2
(b) σ1σ2 / σ1+σ2
(c) 2σ1σ2 / σ1+σ2
(d) σ1+σ2/2σ1σ2

C

Question. A circuit contains an ammeter, a battery of 30 V and a resistance 40.8 ohm all connected in series. If the ammeter has a coil of resistance 480 ohm and a shunt of 20 ohm, the reading in the ammeter will be
(a) 2 A
(b) 1 A
(c) 0.5 A
(d) 0.25 A

C

Question. If current flowing in a conductor changes by 1% then power consumed will change by
(a) 10%
(b) 2%
(c) 1%
(d) 100%

B

Question. Two identical batteries each of e.m.f. 2 V and internal resistance 1 Ω are available to produce heat in an external resistance by passing a current through it. The maximum power that can be developed across R using these batteries is
(a) 3.2 W
(b) 2.0 W
(c) 1.28 W
(d) 8/9 W

B

Question. In an electroplating experiment, m g of silver is deposited when 4 A of current flows for 2 minutes. The amount in g of silver deposited by 6 A of current for 40 seconds will be
(a) 4 m
(b) 2 m
(c) m/2
(d) m/4

C

Question. A steady current of 5 A is maintained for 45 minutes. During this time it deposits 4.572 g of zinc at the cathode of voltameter. E.C.E. of zinc is
(a) 3.387 × 10–4 g/C
(b) 3.387 × 10–4 kg/C
(c) 3.384 × 10–4 kg/C
(d) 3.384 × 10–3 kg/C

A

Question. A heater of 220 V heat a volume of water in 5 minutes time. A heater of 110 V heats the same volume of water in
(a) 5 minutes
(b) 8 minutes
(c) 10 minutes
(d) 20 minutes

D

Question. The resistance of a wire at room temperature 30°C is found to be 10 Ω. Now to increase the resistance by 10%, the temperature of the wire must be [ The temperature coefficient of resistance of the material of the wire is 0.002 per °C]
(a) 36°C
(b) 83°C
(c) 63°C
(d) 33°C

B

Question. The deflection in a galvanometer decreases from 25 divisions to 5 divisions when a resistor of 20Ω is connected in series. Find resistance of galvanometer.
(a) 4 Ω
(b) 5 Ω
(c) 6 Ω
(d) 7 Ω

B

Question. A galvanometer of 50 ohm resistance has 25 divisions. A current of 4 × 10–4 ampere gives a deflection of one division. To convert this galvanometer into a voltmeter having a range of 25 volts, it should be connected with a resistance of
(a) 2450 Ω in series.
(b) 2500 Ω in series.
(c) 245 Ω in series.
(d) 2550 Ω in series.

A

Question. A potentiometer wire, 10 m long, has a resistance of 40Ω. It is connected in series with a resistance box and a 2 V storage cell. If the potential gradient along the wire is 0.1 m V/cm, the resistance unplugged in the box is
(a) 260 Ω
(b) 760 Ω
(c) 960 Ω
(d) 1060 Ω

B

Question. If nealy 105 coulomb are liberated by 1gm equivalent of aluminium, then amount of aluminium (equivalent weight 9) deposited through electrolysis in 20 minutes by a current of 50 ampere will be :
(a) 0.6 gm.
(b) 0.09 gm
(c) 5.4 gm
(d) 10.8 gm