Question

Class 12 Physics MCQ Questions of Current Electricity with Answers?

Answer 1

On this page, you will get significant MCQ Questions for Class 12 Physics. The MCQ Questions for Class 12 with answers have been arranged according to the most recent prospectus and NCERT books and test design proposed in Class 12 by CBSE. Get important Class 12 Physics MCQ Questions of Current Electricity with Answers. The MCQ Questions are vital for the readiness of the forthcoming CBSE Class 12 Physics Board Exam. 

Multiple Choice Questions for a significant piece of exams for class 12 Physics and whenever practiced appropriately can assist you with getting better grades. In an electric circuit, these charges are conveyed by the electrons in the conveyors is known as Current electricity. Ampere is the SI unit of electric flow. These MCQ Questions for Class 12 Physics Current Electricity are likewise valuable for other cutthroat tests like JEE Main Exam.

Practice MCQ Question for Class 12 Physics chapter-wise 

1. An electric heater is connected to the voltage supply. After few seconds, current gets its steady value then its initial current will be

(a) equal to its steady current
(b) slightly higher than its steady current
(c) slightly less than its steady current
(d) zero

2. 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 resis¬tance are same

3. Combine three resistors 5Ω, 4.5Ω and 3Ω in such a way that the total resistance of this combination is maximum

(a) 12.5 Q
(b) 13.5 Q
(c) 14.5 Q
(d) 16.5 Q

4. In parallel combination of n cells, we obtain

(a) more voltage
(b) more current
(c) less voltage
(d) less current

5. In a Wheatstone bridge if 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

6. When a metal conductor connected to left gap of a meter bridge is heated, the balancing point

(a) shifts towards right
(b) shifts towards left
(c) remains unchanged
(d) remains at zero

7. The I-V characteristics shown in figure represents

(a) ohmic conductors
(b) non-ohmic conductors
(c) insulators
(d) superconductors

8. The resistivity of alloy manganin is

(a) Nearly independent of temperature
(b) Increases rapidly with increase in temperature
(c) Decreases with increase in temperature
(d) Increases rapidly with decrease in temperature

9. Specific resistance of ali metals is mostly affected by:

(a) temperature
(b) pressure
(c) magnetic field
(d) volume

10. The example of a non-ohmic resistance is:

(a) copper wire
(b) filament lamp
(c) carbon resistor
(d) diode

11. The specific resistance of a rod of copper as compared to that of thin wire of copper is :

(a) less
(b) more
(c) same
(d) depends upon the length and area of cross-section of the wire

12. Siemen is the unit of:

(a) resistance
(b) conductance
(c) specific conductance
(d) None of these

13. Kirchhoff's first and second laws of electrical circuits are consequences of

(a) conservation of energy
(b) conservation of electrical charge and energy respectively
(c) conservation of electric charge
(d) neither conservation of energy nor electric charge

14. A 5 A fuse wire can with stand a maximum power of 1 W in circuit.The resistance of the fuse wire is:

(a) 0.2 Ω
(b) 5 Ω
(c) 0.4 Ω
(d) 0.04 Ω

15. 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

16. Why is the Wheatstone bridge more accurate than other methods of measuring resistances: ‘

(a) It is a null method
(b) It is based on Kirchhoff's laws
(c) It has four resistances
(d) It does not involve ohm’s law

17. Ohm’s law is valid when the temperature of conductor is :

(a) very low
(b) very high
(c) varying
(d) constant

18. 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

19.  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

20. Which of the following has a negative temperature coefficient of resistance?

(a) Tungsten
(b) Carbon
(c) Nichrome
(d) Platinum

21. Potentiometer measures the potential difference more accurately than a voltmeter because:

(a) It has a wire of high resistance
(b) It has a wire of low resistance
(c) It does not draw current from external circuit
(d) It draws heavy current from external circuit

22. At temperature 0K, the germanium behaves as a / an

(a) conductor
(b) insulator
(c) super-conductor
(d) ferromagnetic

23. 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

24. 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

25. 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.

Answer 2

1. Answer : (b) slightly higher than its steady current

Explanation: When the heater is connected to the supply its initial current will be slightly higher than its steady value but due to heating effect of the current the temperature will rise. This causes an increase in resistance and a slight decrease in current to steady current.

2. Answer : (a) the current through each resistance is same

Explanation: In series combination, current across its circuit components is always constant and in parallel combination the voltage across the circuit components is constant.

3. Answer : (a) 12.5 Q

Explanation: For maximum equivalent or total resistance of the resistors must be combined in series.

R_eq = R₁ + R₂ = R₃ 

= 5 + 4.5 + 3

=12.5Ω

4. Answer : (b) more current

Explanation: In parallel combination of cells the voltage across the terminals is same and resistance is minimum. Therefore, from V = IR. The current drawn from cell combination will be more.

5. Answer : (b) not change

Explanation: The deflection in galvanometer will not be changed due to interchange of battery and the galvanometer.

6. Answer : (a) shifts towards right

Explanation: As the resistance of metal increases on increasing the temperature, so resistance of metal conductor in left arm will increase on heating. For meter bridge,

\(\frac{R_1}{R_2}=\frac{l}{100-l}\)

​​​​​​As R₁ increases I also increases. Hence, balancing point shifts towards right.

7. Answer : (b) non-ohmic conductors

Explanation: The figure is showing I-V characteristics of non-ohmic or non-linear conductors.

8. Answer : (a) Nearly independent of temperature

Explanation: The resistivity of the alloy manganin is (nearly independent of / increases) rapidly with increase of temperature. The resistivity of alloy manganin is nearly independent of temperature. In alloys, the atoms are arranged in a disorderly fashion and hence, they have higher resistivity.

9. Answer : (a) temperature

Explanation: The Specific resistance of metal depends on the temperature of the metal and it increases with increase in temperature. Also, the specific resistance of metals does not vary with a volume of substance, pressure and applied magnetic field.

10. Answer : (d) diode

Explanation: “The resistances which do not obey ohm's law are called non-ohmic resistances.” Two examples: Diode valve triode valve transistors filament of a bulb.

11. Answer : (c) same

Explanation: The resistivity cannot be more or less. Thus, it must be the same and does not depend upon the length and area of the wire. According to above facts, the specific resistance of copper as compared to the thin wire of the copper is independent of the dimension. Hence, it will remain the same.

12. Answer : (b) conductance

Explanation: In SI and in the meter-kilogram-second system, the unit of electrical conductance, admittance, and susceptance. Symbol, S. A conductor has a conductance of 1 siemens if an electrical potential difference of 1 volt produces a 1-ampere current in it.

13. Answer : (b) conservation of electrical charge and energy respectively

Explanation: Kirchhoff's first law of electrical circuit is based on conservation of charge and Kirchhoff's second law of electrical circuit is based on conservation of energy.

14. Answer : (d) 0.04 Ω

Explanation: P =i²R

1 = 25 \(\times\) R

= 0.04 Ω

15.Answer : (b) a high resistance in series 

Explanation: 

16. Answer : (a) It is a null method

Explanation: A Wheatstone's bridge is more accurate than the other methods of measuring resistance because the resistance is obtained using the null method and is based on Kirchoff's law. In the null method, the resistance of the galvanometer and the internal resistance of the cell does not affect the null point.

17.Answer : (d) constant

Explanation: Physical conditions should remain same.

18. Answer : (b) copper has low electrical resistivity

Explanation: Copper is an excellent conductor of electricity, allowing electricity to flow freely through it. As a result, it's employed to form wire connections. Copper has an extremely low electrical resistance when used as a connecting wire.

19. Answer : (d) thermistor

Explanation: A thermisor is a heat sensitive device whose resistivity changes very rapidally with change of temperature. The temperature coefficient of resistivity of a thermistor is very high, which may be positive or negative.

20. Answer : (b) Carbon

Explanation: Semiconductor materials (carbon, silicon, germanium) typically have negative temperature coefficients of resistance.

21. Answer : (c) It does not draw current from external circuit

Explanation: When we measure the emf of a cell by the potentiometer then no current flows in the circuit in zero-deflection condition ie, cell is in open circuit. Thus, in this condition the actual value of a cell is found. In this way, potentiometer is equivaient to an ideal voitmeter of infinite resistance.

22. Answer : (b) insulator

Explanation: n semiconductors i.e. germanium the energy gap is small. Hence at room temperatures some of the valence electrons gain enough thermal energy and jump to the conduction band. Hence we can conclude that at 0K, germanium will behave as an insulator.

23. Answer : (d) high potential

Explanation: When potential difference is applied across an electrolyte, then Ohm's law is obeyed at high potential.

24. Answer : (a) end correction

Explanation: In Meter bridge experiment, it is assumed that the resistance of the L shaped plate is negligible, but actually it is not so. The error created due to this is called end error. To remove this the resistance box and the unknown resistance must be interchanged and then the mean reading must be taken.

25. Answer : (c) Assertion is correct, reason is incorrect

Explanation:  In the absence of external electric field, the free electrons move randomly in the conductor, so their drift velocity is zero and therefore there is no current in the conductor. In the presence of electric field, each electron in the conductor experiences a force in a direction opposite to the electric field. Now the free electrons are drifted from negative end to the positive end of the conductor and hence a current starts to flow in the conductor.

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