MCQ Questions for Class 12 Physics Chapter 3 Download Free PDF: CBSE RBSE and NCERT Physics class 12 MCQs for Chapter 3 “Current Electricity” is very important for the students who want to get good marks. Neet MCQs
MCQ Questions for Class 12 Physics Chapter 3 Current Electricity with PDF
Q.1. In a current carrying conductor the net charge is
(a) 1.6 x 10–19 coulomb
(b) 6.25 x 10–18 coulomb
Q.2. 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
Answer : (c)
Q.3. 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
Answer : (d)
Q.4. A current passes through a wire of nonuniform cross-section. 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
Answer : (d)
Q.5. In the equation AB = C, A is the current density, C is the electric field, Then B is
(c) potential difference
Answer : (a)
Q.6. 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.
Answer : (b)
Q.7. 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
Answer : (d)
Q.8. In the absence of an electric field, the mean velocity of free electrons in a conductor at absolute temperature (T) is
(b) independent of T
(c) proportional to T
(d) proportional to T2
Answer : (a)
Q.9. When a potential difference V is applied across a conductor at a temperature T, the drift velocity of electrons is proportional to
Q.10. For which of the following dependence of drift velocity vd on electric field E, is Ohm’s law obeyed?
(a) vd α E2
(b) vd = E1/2
(c) vd = constant
(d) vd = E
Q.11. The current density (number of free electrons per m3) in metallic conductor is of the order of
Q.12. 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
Q.13. 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
Q.14. 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
Q.15. 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
Q.16. 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
Q.17. 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
Q.18. The effective resistance between C & D in given circuit is
Answer: (c) 2R/3
Q.19. 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
(c) either (a) or (b)
(d) None of these
Q.20. The example of non-ohmic resistance is
(b) copper wire
(c) filament lamp
(d) carbon resistor
Q.21. 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
Q.22. At temperature 0K, the germanium behaves as a / an
Q.23. 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
Q.24. What is the suitable material for electric fuse?
(c) Tin-lead alloy
Q.25. 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
Q.26. 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
Q.27. 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.
Q.28. With increase in temperature the conductivity of
(a) metals increases and of semiconductor decreases.
(b) semiconductors increases and metals decreases.
(c) in both metals and semiconductors increases.
(d) in both metal and semiconductor decreases.
Q.29. 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
Q.30. 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.
Q.31. 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
Q.32. 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.
Q.33. 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.
Q.34. To draw a maximum current from a combination of cells, how should the cells be grouped?
(c) Mixed grouping
(d) Depends upon the relative values of internal and external resistances.
Q.35. The resistance of the coil of an ammeter is R. The shunt required to increase its range n-fold should have a resistance
Q.36. 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
Answer : (c)
Q.37. 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
Q.38. 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
Q.39. 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
Q.40. 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
Q.41. Kirchhoff’s first law, i.e., ∑ i = 0 at a junction, deals with the conservation of
(d) angular momentum
Q.42. The Kirchhoff’s second law (∑iR = ∑E), 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
Q.43. 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 Kirchhoff’s law
(c) It has four resistor arms
(d) It is a null method
Q.44. If in the experiment of Wheatstone’s bridge, the positions of cells and galvanometer are interchanged, then balance point will
(b) remain unchanged
(c) depend on the internal resistance of cell and resistance of galvanometer
(d) None of these
Q.45. 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.
Q.46. 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
Q.47. Potentiometer is based on
(a) deflection method
(b) zero deflection method
(c) both (a) and (b)
(d) None of these
Q.48. 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
Q.49. 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
Q.50. 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.
Q.51. 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
Q.52. 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
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