# CBSE Class 12 Physics Current Electricity MCQs

Refer to CBSE Class 12 Physics Current Electricity MCQs provided below. CBSE Class 12 Physics MCQs with answers available in Pdf for free download. The MCQ Questions for Class 12 Physics with answers have been prepared as per the latest syllabus, CBSE books and examination pattern suggested in Class 12 by CBSE, NCERT and KVS. Multiple Choice Questions for Chapter 3 Current Electricity are an important part of exams for Class 12 Physics and if practiced properly can help you to get higher marks. Refer to more Chapter-wise MCQs for CBSE Class 12 Physics and also download more latest study material for all subjects

## MCQ for Class 12 Physics Chapter 3 Current Electricity

Class 12 Physics students should refer to the following multiple-choice questions with answers for Chapter 3 Current Electricity in Class 12. These MCQ questions with answers for Class 12 Physics will come in exams and help you to score good marks

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

Question: The cold junction of a thermocouple is maintained at 10ºC. No thermo e.m.f. is developed when the hot junction is maintained at 530ºC. The neutral temperature is
(a) 260ºC
(b) 265ºC
(c) 270ºC
(d) 520ºC

Question: Consider a current carrying wire (current I) in the shape of a circle
(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

Question: Two cells of emfs approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm.
(a) The battery that runs the potentiometer should have voltage of 8V.
(b) The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V.
(c) The first portion of 50 cm of wire itself should have a potential drop of 10 V.
(d) Potentiometer is usually used for comparing resistances and not voltages.

Question: Which of the following characteristics of electrons determines the current in a conductor?
(a) Drift velocity alone
(b) Thermal velocity alone
(c) Both drift velocity and thermal velocity
(d) Neither drift nor thermal velocity

Question: The cold junction of a thermocouple is maintained at 10ºC. No thermo e.m.f. is developed when the hot junction is maintained at 530ºC. The neutral temperature is
(a) 260ºC
(b) 265ºC
(c) 270ºC
(d) 520ºC

Question: In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1 kW. The voltage of electric mains is 220 V. The minimum capacity of the main fuse of the building will be:
(a) 8 A
(b) 10 A
(c) 12 A
(d) 14 A

Question: Choose the correct option
Assertion : When current through a bulb decreases by 0.5%, the glow of bulb decreases by 1%.
Reason : Glow (Power) which is directly proportional to square of current
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Question: A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is doubled if
(a) both the length and the radius of the wire are halved.
(b) both the length and the radius of the wire are doubled.
(c) the radius of the wire is doubled.
(d) the length of the wire is doubled.

Question: 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's is :
(a) 5 : 1
(b) 5 : 4
(c) 3 : 4
(d) 3 : 2

Question: Choose the correct option
Assertion : Bending a wire does not effect electrical resistance.
Reason : Resistance of wire is proportional ot resistivity of material.
(a) If both Assertion and Reason are correct and Reasonis the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reasonis not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Question: In a current carrying conductor the net charge is
(a) 1.6 x 10–19 coulomb
(b) 6.25 x 10–18 coulomb
(c) zero
(d) infinite

Question: The current which is assumed to be flowing in a circuit from positive terminal to negative, is called
(a) direct current
(b) pulsating current
(c) conventional current
(d) alternating current

Question: When no current is passed through a conductor,
(a) the free electrons do not move
(b) the average speed of a free electron over a large period of time is not zero
(c) the average velocity of a free electron over a large period of time is zero
(d) the average of the velocities of all the free electrons at an instant is non zero

Question: A current passes through a wire of nonuniform crosssection.
Which of the following quantities are independent of the cross-section?
(a) The charge crossing
(b) Drift velocity
(c) Current density
(d) Free-electron density

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

Question: Drift velocity of electrons is due to
(a) motion of conduction electrons due to random collisions.
(b) motion of conduction electrons due to electric field .E
(c) repulsion to the conduction electrons due to inner electrons of ions.
(d) collision of conduction electrons with each other.

Question: The speed at which the current travels, in conductor, is nearly equal to
(a) 3 × 104 m/s
(b) 3 × 105 m/s
(c) 4 × 106 m/s
(d) 3 × 108 m/s

Question: In the absence of an electric field, the mean velocity of free electrons in a conductor at absolute temperature (T) is
(a) zero
(b) independent of T
(c) proportional to T
(d) proportional to T2

Question: When a potential difference V is applied across a conductor at a temperature T, the drift velocity of electrons is proportional to
(a) V
(b) V
(c) T
(d) T

Question: The current density (number of free electrons per m3) in metallic conductor is of the order of
(a) 1022
(b) 1024
(c) 1026
(d) 1028

Question: A current passes through a resistor. If K1 and K2 represent the average kinetic energy of the conduction electrons and the metal ions respectively then
(a) K1 < K2
(b) K1 : K2
(c) K1 > K2
(d) any of these three may occur

Question: A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it
(a) increases, thermal velocity of the electron increases
(b) decreases, thermal velocity of the electron increases
(c) increases, thermal velocity of the electron decreases
(d) decreases, thermal velocity of the electron decreases

Question: The electric field intensity E, current density J and specific resistance k are related to each other through the relation
(a) E : J/k
(b) E : J k
(c) E : k/J
(d) k : J E

Question: The relaxation time in conductors
(a) increases with the increases of temperature
(b) decreases with the increases of temperature
(c) it does not depends on temperature
(d) all of sudden changes at 400 K

Question: We are able to obtain fairly large currents in a conductor because
(a) the electron drift speed is usually very large
(b) the number density of free electrons is very high and this can compensate for the low values of the electron drift speed and the very small magnitude of the electron charge
(c) the number density of free electrons as well as the electron drift speeds are very large and these compensate for the very small magnitude of the electron charge
(d) the very small magnitude of the electron charge has to be divided by the still smaller product of the number density and drift speed to get the electric current

Question:. In conductor when electrons move between two collisions, their paths are ... A... when external fields are absent and ... B...when external filed is present. Here, A and B refer to
(a) straight lines, straight lines
(b) straight lines, curved lines
(c) curved lines, straight lines
(d) curved lines, curved lines

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

Question: The unit of specific resistance is
(a) Ωm-1
(b) Ω-1m-1
(c) Ω1
(d) 2.5-m-2

Question: The example of non-ohmic resistance is
(a) diode
(b) copper wire
(c) filament lamp
(d) carbon resistor

Question: Constantan wire is used for making standard resistance, because it has
(a) high melting point
(b) low specific resistance
(c) high specific resistance
(d) negligible temperature coefficient of resistance

Question: At temperature 0K, the germanium behaves as a / an
(a) conductor
(b) insulator
(c) super-conductor
(d) ferromagnetic

Question: Which of the following is used for the formation of thermistor?
(a) Copper oxide
(b) Nickel oxide
(c) Iron oxide
(d) All of the above

Question: What is the suitable material for electric fuse?
(a) Cu
(b) Constantan
(d) Nichrome

Question: A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of
(a) each of these increases
(b) each of these decreases
(c) copper strip increases and that of germanium decreases
(d) copper strip decreases and that of germanium increases

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

Question: Nichrome or Manganin is widely used in wire bound standard resistors because of their
(a) temperature independent resistivity
(b) very weak temperature dependent resistivity.
(c) strong dependence of resistivity with temperature.
(d) mechanical strength.

Question: With increase in temperature the conductivity of
(a) metals increases and of semiconductor decreases.
(b) semeconductors increases and metals decreases.
(c) in both metals and semiconductors increases.
(d) in both metal and semiconductor decreases.

Question: The resistance of a metal increases with increasing temperature because
(a) the collisions of the conducting electrons with the electrons increase
(b) the collisions of the conducting electrons with the lattice consisting of the ions of the metal increase
(c) the number of conduction electrons decreases
(d) the number of conduction electrons increases

Question: To minimise the power loss in the transmission cables connecting the power stations to homes and factories, the transmission cables carry current
(a) at a very low voltage.
(b) at a very high voltage
(c) at 220 volt
(d) neither at a very high voltage nor at a very low voltage.

Question: Appliances based on heating effect of current work on
(a) only a.c.
(b) only d.c.
(c) both a.c. and d.c.
(d) None of these

Question: In the series combination of two or more than two resistances
(a) the current through each resistance is same
(b) the voltage through each resistance is same
(c) neither current nor voltage through each resistance is same
(d) both current and voltage through each resistance are same.

Question: Two or more resistors are said to be in ...A... if one end of all resistors is joined together and similarly the other ends joined together, Here, A refers to
(a) series
(b) parallel
(c) either (a) or (b)
(d) None of these

Question: Emf of a cell is
(a) the maximum potential difference between the terminals of a cell when no current is drawn from the cell.
(b) the force required to push the electrons in the circuit.
(c) the potential difference between the positive and negative terminal of a cell in a closed circuit.
(d) less than terminal potential difference of the cell.

Question: When potential difference is applied across an electrolyte, then Ohm’s law is obeyed at
(a) zero potential '
(b) very low potential
(c) negative potential
(d) high potential

Question:  To draw a maximum current from a combination of cells, how should the cells be grouped?
(a) Parallel
(b) Series
(c) Mixed grouping
(d) Depends upon the relative values of internal and external resistances.

Question: Under what condition will the strength of current in a wire of resistance R be the same for connection is series and in parallel of n identical cells each of the internal resistance r?
When
(a) R : n r
(b) R : r/n
(c) R : r
(d) R → ∞, r →0

Question: A cell of internal resistance r is connected to an external resistance R. The current will be maximum in R, if
(a) R : r
(b) R < r
(c) R > r
(d) R : r/2

Question: An energy source will supply a constant current into the load if its internal resistance is
(a) very large as compared to the load resistance
(b) equal to the resistance of the load
(c) non-zero but less than the resistance of the load
(d) zero

Question: Sensitivity of potentiometer can be increased by
(a) increasing the e.m.f of the cell
(b) increasing the length of the potentiometer
(c) decreasing the length of the potentiometer wire
(d) None of these

Question: In potentiometer a balance point is obtained, when
(a) the e.m.f. of the battery becomes equal to the e.m.f of the experimental cell
(b) the p.d. of the wire between the +ve end of battery to jockey becomes equal to the e.m.f. of the experimental cell
(c) the p.d. of the wire between +ve point of cell and jockey becomes equal to the e.m.f. of the battery
(d) the p.d. across the potentiometer wire becomes equal to the e.m.f. of the battery

Question: In the experiment of potentiometer, at balance point, there is no current in the
(a) main circuit
(b) galvanometer circuit
(c) potentiometer circuit
(d) both main and galvanometer circuits

Question: The internal resistance of dry cell is ...A..., than the internal resistance of common electrolytic cell. Here, A refers to
(a) much lower
(b) much higher
(c) slightly lower
(d) slightly higher

Question: Kirchoff’s first law, i.e., S i : 0 at a junction, deals with the conservation of
(a) charge
(b) energy
(c) momentum
(d) angular momentum

Question: The Kirchhoff's second law (ΣiR : ΣE), where the symbols have their usual meanings, is based on
(a) conservation of momentum
(b) conservation of charge
(c) conservation of potential
(d) conservation of energy

Question: Why is the Wheatstone bridge better than the other methods of measuring resistances?
(a) It does not involve Ohm’s law
(b) It is based on Kirchoff’s law
(c) It has four resistor arms
(d) It is a null method

Question: If in the experiment of Wheatstone’s bridge, the positions of cells and galvanometer are interchanged, then balance point will
(a) change
(b) remain unchanged
(c) depend on the internal resistance of cell and resistance of galvanometer
(d) None of these

Question: In a wheatstone bridge in the battery and galvanometer are interchanged then the deflection in galvanometer will
(a) change in previous direction
(b) not change
(c) change in opposite direction
(d) none of these.

Question: In meter bridge or Wheatstone bridge for measurement of resistance, the known and the unknown resistance are interchanged. The error so removed is
(a) end correction
(b) index error
(c) due to temperature effect
(d) random error

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 potentiometer almost draws no current during measurement.
(d) range of the voltmeter is not as wide as that of the potentiometer.

Question: A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves
(b) A condition of no current flow through the galvanometer
(c) A combination of cells, galvanometer and resistances
(d) Cells

Question: Choose the correct option
Assertion : Kirchoff¢s junction rule follows fromconservation of charge.
Reason : Kirchoff¢s loop rule follows from conservation of momentum
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Question: Which of the following statements is false ?
(a) A rheostat can be used as a potential divider
(b) Kirchhoff's second law represents energy conservation
(c) Wheatstone bridge is the most sensitive when all the four resistances are of the same order of magnitude
(d) In a balanced wheatstone bridge if the cell and the galvanometer are exchanged, the null point is disturbed.

Question: Choose the correct option
Assertion : A current flows in a conductor only when there is an electric field within the conductor.
Reason : The drift velocity of electron in presence of electric field decreases.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Question: Ten identical cells connected in series are needed to heat a wire of length one meter and radius ‘r’ by 10ºC in time ‘t’. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time ‘t’?
(a) 10
(b) 20
(c) 30
(d) 40

Question: An electric heating element in vacuum is surrounded by a cavity at constant temperature of 227ºC; it consumes 60W of power to maintain a temperature of 727ºC. What is the power consumed by the element to maintain a temperature of 1227º C?
(a) 101 W
(b) 304 W
(c) 90 W
(d) 320 W

Question: An electrical cable of copper has just one wire of radius 9 mm. Its resistance is 5 ohm. This single copper wire of the cable is replaced by 6 different well insulated copper wires each of radius 3 mm. The total resistance of the cable will now be equal to
(a) 7.5 ohm
(b) 45 ohm
(c) 90 ohm
(d) 270 ohm

Question: A hank of uninsulated wire consisting of seven and a half turns is stretched between two nails hammered into a board to which the ends of the wire are fixed. The resistance of the circuit between the nails is determined with the help of electrical measuring instruments. Determine the proportion in which the resistance will change if the wire is unwound so that the ends remain to be fixed to the nails.
(a) 225
(b) 15
(c) 240
(d) 250

Question: To get maximum current in a resistance of 3 ohms, one can use n rows of m cells (connected in series) connected in parallel. If the total number of cells is 24 and the internal resistance of a cell is 0.5 ohms then
(a) m : 12, n : 2
(b) m : 8, n : 3
(c) m : 2, n : 12
(d) m : 6, n : 4

Question: An Aluminium (Al) rod with area of cross-section 4 × 10–6 m2 has a current of 5 ampere. Flowing through it. Find the drift velocity of electron in the rod. Density of Al : 2.7 × 103 kg/m3 and Atomic wt. : 27. Assume that each Al atom provides one electron
(a) 8.6 × 10–4 m/s
(b) 1.29 × 10–4 m/s
(c) 2.8 × 10–2 m/s
(d) 3.8 × 10–3 m/s

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