# MCQs for Physics Class 12 with Answers Chapter 3 Current Electricity

Students of class 12 Physics should refer to MCQ Questions Class 12 Physics Current Electricity with answers provided here which is an important chapter in Class 12 Physics NCERT textbook. These MCQ for Class 12 Physics with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 12 Physics. The following MCQs can help you to practice and get better marks in the upcoming class 12 Physics examination

## Chapter 3 Current Electricity MCQ with Answers Class 12 Physics

MCQ Questions Class 12 Physics Current Electricity provided below have been prepared by expert teachers of grade 12. These objective questions with solutions are expected to come in the upcoming Standard 12 examinations. Learn the below provided MCQ questions to get better marks in examinations.

Question. Two resistors of resistance R1 and R2 having R1 > R2 are connected in parallel. For equivalent resistance R, the correct statement is:
(a) R > R1 + R2
(b) R1 < R1 < R2
(c) R2 < R1 < (R1 + R2)
(d) R < R2 < R1

D

Question. The current in the adjoining circuit will be

C

Question. Dimensions of a block are 1cm × 1cm × 100 cm. If specific resistance of its material is 3 × 10–7 Ω m, then the resistance between the opposite rectangular faces is
(a) 3 × 10–9 Ω
(b) 3 × 10–7 Ω
(c) 3 × 10–5 Ω
(d) 3 × 10–3 Ω

B

Question. In the figure a carbon resistor has bands of different colours on its body as mentioned in the figure. The value of the resistance is

(a) 24 × 106 Ω ± 5%
(b) 35 × 106 Ω ± 10%
(c) 5.6 k Ω
(d) 24 × 105 Ω ± 10%

D

Question. A cell of emf E and internal resistance r is connected across an external resistor R. The graph showing the variation of P.D. across R versus R is

A

Question. In a Wheatstone bridge, all the four arms have equal resistance R. If resistance of the galvanometer arm is also R, then equivalent resistance of the combination is
(a) R
(b) 2R
(c) R/2
(d) R/4

A

Question. Two electric bulbs whose resistance are in the ratio 1 : 2 are arranged in parallel to a constant voltage source. The powers dissipated in them have the ratio
(a) 1 : 2
(b) 1 : 1
(c) 2 : 1
(d) 1 : 4

C

Question. A potentiometer is an accurate and versatile device to make electrical measurement of EMF because the method involves
(b) a condition of no current flow through the galvanometer
(c) a combination of cells, galvanometer and resistance
(d) cells

B

Question. A battery of e.m.f. 10 V and internal resistance 0.5 W is connected across a variable resistance R. The value of R for which the power delivered in it is maximum is given by
(a) 0.5 Ω
(b) 1.0 Ω
(c) 2.0 Ω
(d) 0.25 Ω

A

Question. Two wires A and B of the same material, having radii in the ratio 1 : 2 and carry currents in the ratio 4 : 1. The ratio of drift speed of electrons in A and B is
(a) 16 : 1
(b) 1 : 16
(c) 1 : 4
(d) 4 : 1

A

Question. An ammeter has a resistance of G ohm and a range of I amp. The value of resistance used in parallel to convert it into an ammeter of range nI amp is
(a) nG
(b) (n – 1)G
(c) G/n
(d) G/(n – 1)

D

Question. Consider a current carrying wire (current I ) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is
(a) source of emf.
(b) electric field produced by charges accumulated on the surface of wire.
(c) the charges just behind a given segment of wire which push them just the right way by repulsion.

B

Question. Figure represents a part of a closed circuit. The potential difference between points A and B (VA – VB) is

(a) +9 V
(b) – 9 V
(c) +3 V
(d) + 6 V

A

Question. Two batteries of emf ε1 and ε22 > ε1) and internal resistances r1 and r2 respectively are connected in parallel as shown in Figure.
(a) The equivalent emf εeq of the two cells is between e1 and e2, i.e., ε1< εeq < ε2
(b) The equivalent emf εeq is smaller than ε1.
(c) The εeq is given by εeq = ε1 + ε2 always.
(d) εeq is independent of internal resistances r1 and r2.

A

Question. A student connects 10 dry cells each of emf E and internal resistance r in series, but by mistake the one cell gets wrongly connected. Then net emf and net internal resistance of the combination will be
(a) 8E, 8r
(b) 8E, 10r
(c) 10E, 10r
(d) 8E,(r/10)

B

Question. A metal rod of length 10 cm and a rectangular cross-section of 1cm × 1 / 2 cm is connected to a battery across opposite faces. The resistance will be
(a) maximum when the battery is connected across 1 cm × 1 / 2 cm faces.
(b) maximum when the battery is connected across 10 cm × 1 cm faces.
(c) maximum when the battery is connected across 10 cm × 1 / 2 cm faces.
(d) same irrespective of the three faces.

A

Question. The emf developed by a thermocouple is measured with the help of a potentiometer and not by a moving coil millivoltmeter because
(a) the potentiometer is more accurate than the voltmeter
(b) the potentiometer is more sensitive than voltmeter
(c) the potentiometer makes measurement without drawing any current from the thermocouple
(d) measurement using a potentiometer is simpler than with a voltmeter

C

Question. In the given circuit, as the sliding contact C is moved from A to B

(a) the readings of both the ammeter and the voltmeter remain constant
(b) the reading of both the ammeter and the voltmeter increase
(c) the reading of the ammeter remains constant but that of the voltmeter increases
(d) the reading of the ammeter remains constant but that of the voltmeter decreases

C

Question. The resistivity of iron is 1 ×10–7 ohm-meter. The resistance of the given wire of a particular thickness and length is 1 ohm. If the diameter and length of the wire both are doubled the resistivity will be (in ohm-meter)
(a) 1 ×10–7
(b) 2 ×10–7
(c) 4 ×10–7
(d) 8 ×10–7

A

Question. Temperature dependence of resistivity r (T) of semiconductors insulators and metals is significantly based on the following factors.
(a) Number of charge carriers can change with temperature T.
(b) Time interval between two successive collision can depend on T.
(c) Length of material can be a function of T.
(d) Mass of carriers is a function of T.

A, B

Question. Potentiometer measures potential more accurately because
(a) it measures potential in open circuit
(b) it uses sensitive galvanometer for null deflection
(c) it uses high resistance potentiometer wire
(d) it measures potential in closed circuit

A

Question. Coils in the resistance boxes are made from doubled up insulated wires
(a) to cancel the effect of self induction
(b) to nullify the heating effect
(c) to nullify the Peltier effect
(d) to reduce effective length of the wire

A

Question. For measuring voltage of any circuit, potentiometer is preferred to voltmeter because
(a) the potentiometer is cheap and easy to handle.
(b) calibration in the voltmeter is sometimes wrong .
(c) the potential draws no current during measurement.
(d) range of the voltmeter is not as wide as that of the potentiometer.

C

Question. Two identical fuses are rated at 10 A. If they are joined
(A) in parallel, the combination acts as a fuse of rating 20 A
(B) in parallel, the combination acts as a fuse of rating 5 A
(C) in series, the combination acts as a fuse of rating 10 A
(D) in series, the combination acts as a fuse of rating 20 A
Select the correct options.
(a) A, B
(b) A, C
(c) B, D
(d) B, C, D

B

Question. The resistance of the coil of an ammeter is R. The shunt required to increase its range n-fold should have a resistance
(a) R/n
(b) R/n – 1
(c) R/n + 1
(d) nR

B

Question. A cell of internal resistance r is connected across an external resistance nr. Then the ratio of the terminal voltage to the emf of the cell is

C

Question. Who among the following scientists made the statement ? “Chemical change can produce electricity”.
(a) Galvani
(c) Coulomb
(d) Thompson

A

Question. An electric kettle has two heating coils. When one of the coils is connected to an a.c. source, the water in the kettle boils in 10 minutes. When the other coil is used the water boils in 40 minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be
(a) 15 min
(b) 8 min
(c) 4 min
(d) 25 min

B

Question. Two 220 volt, 100 watt bulbs are connected first in series and then in parallel. Each time the combination is connected to a 220 volt a.c. supply line. The power drawn by the combination in each case respectively will be
(a) 50 watt, 200 watt
(b) 50 watt, 100 watt
(c) 100 watt, 50 watt
(d) 200 watt, 150 watt

A

Question. The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 W is
(a) 0.5 Ω
(b) 0.8 Ω
(c) 1.0 Ω
(d) 0.2 Ω

A

Question. Kirchhoff ’s junction rule is a reflection of
(a) conservation of current density vector.
(b) conservation of charge.
(c) the fact that the momentum with which a charged particle approaches a junction is unchanged (as a vector) as the charged particle leaves the junction.
(d) the fact that there is no accumulation of charged at a junction.

B, D

Question. A current source drives a current in a coil of resistance R1 for a time t. The same source drives current in another coil of resistance R2 for same time. If heat generated is same, find internal resistance of source.

D

Question. Which of the following is not reversible ?
(a) Joule effect
(b) Peltier effect
(c) See beck effect
(d) Thomson effect

A

Question. In which of the following the power dissipation is proportional to the square of the current ?
(a) Peltier effect
(b) Joule’s effect
(c) Thomson effect
(d) None of the above

B

Question. When current is passed through a junction of two dissimilar metals, heat is evolved or absorbed at the junction. This process is called
(a) See beck effect
(b) Joule effect
(c) Peltier effect
(d) Thomson effect

C

Question. A 4 ohm resistance wire is bent through 180º at its mid point and the two halves are twisted together. Then the resistance is
(a) 1 Ω
(b) 2 Ω
(c) 5 Ω
(d) 8 Ω

A

Question. Which of the following in electricity is analogous to momentum mv in dynamics ?
(a) IV
(b) I L
(c) Q L
(d) IQ

B

Question. You are given a resistance coil and a battery. In which of the following cases is largest amount of heat generated ?
(a) When the coil is connected to the battery directly
(b) When the coil is divided into two equal parts and both the parts are connected to the battery in parallel
(c) When the coil is divided into four equal parts and all the four parts are connected to the battery in parallel
(d) When only half the coil is connected to the battery

C

Question. If R1 and R2 are respectively the filament resistances of a 200 watt bulb and a 100 watt bulb designed to operate on the same voltage
(a) R1 is two times R2
(b) R2 is two times R1
(c) R2 is four times R1
(d) R1 is four times R2

B

Question. A torch bulb rated as 4.5 W, 1.5 V is connected as shown in fig. The e.m.f. of the cell, needed to make the bulb glow at full intensity is

(a) 4.5 V
(b) 1.5 V
(c) 2.67 V
(d) 13.5 V

D

Question. In a metre bridge, the balancing length from the left end (standard resistance of one ohm is in the right gap) is found to be 20 cm. The value of the unknown resistance is
(a) 0.8 Ω
(b) 0.5 Ω
(c) 0.4 Ω
(d) 0.25 Ω

D

Question. An electric fan and a heater are marked as 100 W, 220 V and 1000 W, 220 V respectively. The resistance of heater is
(a) equal to that of fan
(b) lesser than that of fan
(c) greater than that of fan
(d) zero

B

Question. In a neon gas discharge tube Ne+ ions moving through a cross-section of the tube each second to the right is 2.9 × 1018, while 1.2 × 1018 electrons move towards left in the same time; the electronic charge being 1.6 × 10–19 C, the net electric current is
(a) 0.27 A to the right
(b) 0.66 A to the right
(c) 0.66 A to the left
(d) zero

B

Question. A wire X is half the diameter and half the length of a wire Y of similar material. The ratio of resistance of X to that of Y is
(a) 8 : 1
(b) 4 : 1
(c) 2 : 1
(d) 1 : 1

C

Question. 2, 4 and 6 S are the conductances of three conductors. When they are joined in series, their equivalent conductance will be
(a) 12 S
(b) (1/12) S
(c) (12/11) S
(d) (11/12) S

C

Question. 2, 4 and 6 S are conductances of three conductors. When they are joined in parallel, their equivalent conductance will be
(a) 12 S
(b) (1/12) S
(c) (12/11) S
(d) (11/12) S

A

Question. Two identical cells connected in series send 1.0A current through a 5 W resistor. When they are connected in parallel, they send 0.8 A current through the same resistor. What is the internal resistance of the cell?
(a) 0.5 Ω
(b) 1.0 Ω
(c) 1.5 Ω
(d) 2.5 Ω

D

Question. If negligibly small current is passed though a wire of length 15 m & resistance of 5Ω, having uniform cross section of 6 × 10–7 m2, then coefficient of resistivity of material is
(a) 1×10–7 Ω–m
(b) 2×10–7 Ω–m
(c) 3×10–7 Ω–m
(d) 4×10–7 Ω–m

B

Question. A potentiometer consists of a wire of length 4m and resistance 10Ω. It is connected to a cell of e.m.f. 3V. The potential gradient of wire is
(a) 5V/m
(b) 2V/m
(c) 5V/m
(d) 10V/m

A

Question. Potentiometer wire of length 1 m is connected in series with 490Ω resistance and 2 V battery. If 0.2 mV/cm is the potential gradient, then resistance of the potentiometer wire is
(a) 4.9 Ω
(b) 7.9 Ω
(c) 5.9 Ω
(d) 6.9 Ω

A

Question. In the equation AB = C, A is the current density, C is the electric field, Then B is
(a) resistivity
(b) conductivity
(c) potential difference
(d) resistance

A

Question. Two wires of same metal have the same length but their cross-sections are in the ratio 3 : 1. They are joined in series. The resistance of the thicker wire is 10 Ω. The total resistance of the combination is
(a) 5/2 Ω
(b) 40/3 Ω
(c) 40 Ω
(d) 100 Ω

C

Question. An electric lamp is marked 60 W, 220 V. The cost of kilo watt hour of electricity is Rs. 1.25. The cost of using this lamp on 220 V for 8 hours is
(a) Re 0.25
(b) Re 0.60
(c) Re 1.20
(d) Re 4.00

B

Question. The electrochemical equivalent of a metal is 3.3 × 10–7 kg per coulomb. The mass of the metal liberated at the cathode when a 3 A current is passed for 2 seconds will be
(a) 19.8 × 10–7 kg
(b) 9.9 × 10–7 kg
(c) 6.6 × 10–7 kg
(d) 1.1 × 10–7 kg

A

Question. A 4 m long wire of resistance 8 Ω is connected in series with a battery of e.m.f. 2 V and a resistor of 7 Ω. The internal resistance of the battery is 1 Ω. What is the potential gradient along the wire?
(a) 1.00 V m–1
(b) 0.75 V m–1
(c) 0.50 V m–1
(d) 0.25 V m–1

D

Question. A wire has a resistance 12 Ω. It is bent in the form of a circle. The effective resistance between two points on any diameter is
(a) 6 Ω
(b) 3 Ω
(c)12 Ω
(d) 24 Ω

B

Question. A leclanche cell supplies a current of one ampere for ten minutes. The electreochemical equivalent of hydrogen = 0.00001014 gram per coulomb. The mass of hydrogen liberated is :
(a) 0.00625 g
(b) 0.01248 g
(c) 0.01872 g
(d) 0.02496 g.

A

Question. Three equal resistors connected across a source of e.m.f. together dissipate 10 watt of power. What will be the power dissipated in watt if the same resistors are connected in parallel across the same source of e.m.f.?
(a) 10/3
(b) 10
(c) 30
(d) 90

D

Question. Two 1000 W heaters when connected in parallel across 220 V supply produced heat QP in time t. If they are connected in series across the same power supply the heat produced in the same time is QS. What is QP/QS?
(a) 4
(b) 2
(c) 0.5
(d) 0.25.

A

Question. If 25W, 220 V and 100 W, 220 V bulbs are connected in series across a 440 V line, then
(a) only 25W bulb will fuse
(b) only 100W bulb will fuse
(c) both bulbs will fuse
(d) None of these