# Current Electricity MCQ | Class 12 | Physics | Chapter 3

## Current Electricity MCQ Chapter 3

Electric current is the rate of flow of negative charges in a conductor.

Below are some of the very important NCERT Current Electricity MCQ Class 12 Physics Chapter 3 with answers. These Current Electricity MCQ have been prepared by expert teachers and subject experts based on the latest syllabus and pattern of CBSE Term 1 examination.

We have given these Current Electricity MCQ Class 12 Physics Questions with Answers to help students understand the concept.

MCQ Questions for Class 12 Physics are very important for the latest CBSE Term 1 and Term 2 pattern. These MCQs are very important for students who want to score high in CBSE Board, NEET and JEE exam.

We have put together these NCERT MCQ Questions of Current Electricity for Class 12 Physics Chapter 3 with Answers for the practice on a regular basis to score high in exams. Refer to these MCQs Questions with Answers here along with a detailed explanation.

## MCQ

1 . The relaxation time in conductors

1. increases with increase in temperature
2. decreases with increase in temperature
3. it does not depend on temperature
4. all of sudden changes at 400 Kelvin

2. A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of of the electron in it

1. increases, thermal velocity of electron increases
2. decreases, thermal velocity of electron increases
3. increases, thermal velocity of electron decreases
4. decreases, thermal velocity of electron decreases

3. Drift velocity of a free electron inside a conductor is

1. the thermal speed of the free electron
2. the speed with which a free electron emerges out of the conductor
3. the average speed required by the electron in any direction
4. the average speed of the electron between successive collisions in the direct opposition to opposite to the applied electric field

4. The electric resistance of a certain wire of iron is R if its length and radius are both doubled then

1. the radius and the specific radius resistance will both remain unchanged
2. the resistance will be doubled, then the specific resistance will be halved
3. the resistance will be halved, and the specific resistance will remain unchanged
4. the resistance will be halved, and then the specific resistance will be doubled

5. When no current is passed through a conductor

1. the free electrons do not move
2. the average speed of a free electron over a large period of time is not zero
3. the average velocity of a free electron over a large period of time is zero
4. the average of the velocities of all the free electrons at an instant is non zero

6. The time rate of flow of charge through any cross section of a conductor

1. Electric potential
2. Electric current
3. Electric intensity
4. Electric charge

7. When a current I is set up in a wire of radius r, the drift velocity is vd. If the same current is set up through a wire of radius 2r, the drift velocity will be

1. 4vd
2. 2vd
3. vd/2
4. vd/4

8. If a current of 0.5 A flows in a 60 W lamp, then the total charge passing through it in two hours will be

1. 1800 C
2. 2400 C
3. 3000 C
4. 3600 C

9. Two wires A and B of the same material, having radii in the ratio 1:2 and carrying currents in the ratio 4:1. The ratio of drift speed of electrons in A and B

1. 16:1
2. 1:16
3. 1:4
4. 4:1

10. In a potentiometer experiment, when the galvanometer shows no deflection, then no current flows through

1. Potentiometer wire
2. Galvanometer circuit
3. Main circuit
4. Battery

11. In a wheatstone bridge in the battery and galvanometer are interchanged then the deflection in galvanometer will

1. Change in previous direction
2. Not change
3. Change in opposite direction
4. None of these

12. Ohm’s law is valid when the temperature of the conductor is ___________

1. Constant
2. Very high
3. Very low
4. Varying

13. A wire has a non-uniform cross-section as shown in the figure. If a steady current is flowing through it, then the drift speed of the electrons

1. Is constant throughout the wire
2. Decreases from A and B
3. Increases from A and B
4. Varies randomly

14. A wire of resistance 4Ω is stretched to twice its original length. The resistance of stretched wire would be

1. 16Ω

15. The instrument among the following which measures the emf of a cell most accurately is

1. A voltmeter
2. An ammeter
3. Potentiometer
4. Post office box

Click Below To Learn Chemistry Term-1 Syllabus Chapters MCQs

16. In meter bridge or wheatstone bridge for measurement of resistance, the known and the unknown and the unknown resistance are interchanged. The error so removed is

1. End correction
2. Index error
3. Due to temperature effect
4. Random error

17. In a closed circuit, the vector sum of total emf is equal to the sum of the ___________

1. Currents
2. Resistance
3. Products of currents and the resistance
4. Products of potential differences

18. Kirchhoff’s second law is based on the law of conservation of

1. Charge
2. Energy
3. Momentum
4. Sum of mass and energy

19. Kirchhoff’s first law at a junction is based on the law of conservation of

1. Charge
2. Energy
3. Momentum
4. Angular momentum

20. When the length and area of cross-section both are doubled, then its resistance

1. Will become half
2. Will be doubled
3. Will remain the same
4. Will become four times

21. For a metallic wire, their ratio V/I

1. Is independent of temperature
2. Increases as the temperature rises
3. Decreases as the temperature rises
4. Increases or decreases as temperature rises, depending upon the metal

22. A certain wire has resistance R. The resistance of another wire identical with the first except having twice its diameter is

1. 2R
2. 0.25R
3. 4R
4. 0.5R

23. The resistance of a straight conductor does not depend upon it

1. Temperature
2. Length
3. Material
4. Shape of cross-section

24. In meter bridge or wheatstone bridge for measurement of resistance, the known and the unknown resistance are interchanged. The error so removed is

1. End correction
2. Index error
3. Due to temperature effect
4. Random error

25. Two cells of emf’s approximately 5V and 10V are to be accurately compared using a potentiometer of length 400cm

1. The battery that runs the potentiometer should have voltage of 8V
2. The battery of potentiometer can have a voltage of 15V and R adjusted so that the potential drop across the wire slightly exceeds 10V
3. The first portion of 50 cm of wire itself should have a potential drop of 10V
4. Potentiometer is usually used for comparing resistance are not voltages

26. Which of the following characteristics of electrons determines the current in a conductor?

1. Drift velocity alone
2. Thermal velocity alone
3. Both drift velocity and thermal velocity
4. Neither drift nor thermal velocity

27. A potential difference of 10 V is applied across a conductor of length 0.1 m. If the drift velocity of electrons is 2 x 10-4 m/s, the electron mobility is ________ m2V-1s-1

1. 1 x 10-6
2. 2 x 10-6
3. 3 x 10-6
4. 4 x 10-6

28. In wheatstone bridge, three resistors P, Q, R are connected in three arms in order and 4th arm S is formed by two resistors S1 and S2 connected in parallel. The condition for bridge to be balanced is P/Q

1. R(S1+S2) / S1S2
2. S1S2 / R(S1+S2)
3. RS1S2 / (S1 + S2)
4. (S1 + S2) / RS1S2

29. According to kirchoff’s law, in any analytical circuit. If the direction of current is assumed opposite, then the value of current will be

1. i
2. 2i
3. -i
4. 0

30. Consider a current carrying wire 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

1. Source of emf
2. Electric field produced by charges accumulated on the surface of wire
3. The charges just behind a given segment of wire which push them just the right way by repulsion
4. The charges ahead

31. The reciprocal of resistance is

1. Conductance
2. Voltage
3. Resistivity
4. Reactance

32. A potential difference V is applied to a copper wire. If the potential difference is increased to 2V, then the drift velocity of electrons will

1. Be double the initial velocity
2. Remain same
3. Be √2 times the initial velocity
4. Be half the initial velocity

33. Power dissipated in the circuit shown in the figure. The value of R is

1. 15Ω
2. 10Ω
3. 20Ω

34. A 100W, 200V bulb is connected to a 160V supply. The actual power consumption would be

1. 185W
2. 100W
3. 54W
4. 64W

35. How many electrons constitute the current of one micro ampere in one second?

1. 6.25 x 108
2. 6.25 x 1012
3. 6.25 x 109
4. 6.25 x 1015

36. Which of the following is not the advantage of carbon resistors?

1. It is small in size and is light in weight
2. It has low-temperature coefficient value
3. Using it high-value resistor can easily be made
4. It has high a power rating with a low tolerance value

37. The length of a potentiometer wire is l. A cell of emf E is balanced at a length l/3 from the positive end of the wire. If the length of the wire is increased by l/2. At what distance will the same cell give a balance point?

1. 2l / 3
2. l / 2
3. l / 6
4. 4l / 3

38. In a meter bridge setup, which of the following should be the properties of the one meter long wire?

1. High resistivity and low temperature coefficient
2. Low resistivity and low temperature coefficient
3. Low resistivity and high temperature coefficient
4. High resistivity and high temperature coefficient

39. Four conductors of resistance 4, 3, 9 and 6 ohm are connected in AB, BC, CD and DA arms of a wheatstone bridge. The bridge can be balanced by connecting

1. 6 ohm in series with 3 ohm conductor
2. 4 ohm in parallel with 6 ohm conductor
3. 3 ohm in series with 3 ohm conductor
4. 5 ohm in series with 6 ohm conductor

40. Two cells each of electromotive force E and internal resistance r are connected in parallel across the resistance R. The maximum energy given to the resistor per second if

1. R = r/2
2. R = r
3. R = 2r
4. R = 0

41. The resistance of a wire at temperature t°C and 0°C are relatable by

1. Rt = R0 ( 1 + ɑt )
2. Rt = R0 ( 1 – ɑt )
3. Rt = R02 ( 1 + ɑt )
4. Rt = R02 ( 1 – ɑt )

42. The resistance of resistance R is connected to 25V supply and heat produced in it 25J sec. The value of R is

1. 225Ω
2. 25Ω
3. 50Ω

43. The temperature coefficient of resistance of a wire is 0.00125per°C. At 300K, its resistance is 1Ω. This resistance of the wire will be 2Ω at

1. 1154K
2. 1100K
3. 1400K
4. 1127K

44. Three resistances R1, R2 and R3 (R1 > R2 > R3) are connected in series. If current I1, I2 and I3 respectively is flowing through them, the correct relation will be

1. I1 = I2 = I3
2. I1 > I2 > I3
3. I1 < I2 < I3
4. I1 > I2 < I3

45. How many resistors of 176Ω should be connected in parallel to get 5A current from 220 V supply

1. 2
2. 3
3. 6
4. 4

### Current Electricity MCQAnswers

1 . (2) 2. (2) 3. (4) 4. (3) 5. (4) 6. (2) 7. (4) 8. (4) 9. (1) 10. (3) 11. (2) 12. (1) 13. (2) 14. (4) 15. (3) 16. (1) 17. (3) 18. (2) 19. (1) 20. (3) 21. (2) 22. (2) 23. (4) 24. (1) 25. (2) 26. (1) 27. (2) 28. (1) 29. (3) 30. (2) 31. (1) 32. (1) 33. (4) 34. (4) 35. (2) 36. (4) 37. (2) 38. (1) 39. (3) 40. (1) 41. (1) 42. (3) 43. (2) 44. (1) 45. (4)

## Assertion-Reason Based MCQ

Codes

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true and but R is not a correct explanation of A

(c) A is true but R is false

(d) A is false, but R is true

1 . Assertion Current density at any point is ohmic resistor is in direction of electric field at that point.

Reason A point charge when released from rest in a region having only electric field always move along electric lines of force.

2. Assertion The 200 watt bulb glow with more brightness than hundred watt bulb.

Reason 100 watt bulb has more resistance than a 200 watt bulb.

3. Assertion bending a wire does not affect electrical resistance.

Reason resistance of wire is proportional to resistivity of material.

4. Assertion Fuse wire must have high resistance and low melting point.

Reason Fuse is used for small current flow only.

5. Assertion Two electric bulbs of 50 Watt and hundred what are given when connected in series 50 Watt bulb glows more but when connected in parallel hundred watt bulb glows more.

Reason In series combination power is directly proportional to the resistance of the circuit but in parallel combination power is inversely proportional to the resistance of the circuit.

6. 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.

7. Assertion Two bulbs of some wattage, one having a carbon filament and the other having a metallic filament are connected in series. Metallic bulbs will glow more brightly than carbon filament bulb.

Reason Carbon is a semiconductor

Assertion-Reason Based MCQ Answers

1 . (c)

From the relation j = σE the current density j at any point in ohmic resistor is in direction of electric field E at that point. In space having non-uniform electric field, charges released from rest may not move along electric line of force.

2. (a)

P = V2 / R

R = V2 / P

R ∝ 1 / P

Higher the power of bulb, lesser will be the resistance and thus, the bulb will glow more.

3. (a)

When wire is bent, the resistivity, length and area do not change and thus, the resistance also remains unchanged.

4. (3)

Fuse wire should have high resistance because in series, current remains same, therefore according to Joule’s law,

H = (I2Rt / 4.2) cal

Heat produced is high if R is high. The melting point must be low so that wire may melt with increase in temperature. As the current equal to maximum safe value, flows through the fuse wire, it heats up, melts and break the circuit.

5. (1)

Resistance of 50W bulb is two times the resistance of 100W bulb. When bulbs are connected in series, 50W bulb will glow more as P = I2R. In parallel, the 100W bulb will glow more as P = V2/R.

6. (1)

Glow = Power = I2R

dP/P = 2(dI/I) = 2 x 0.5 = 1%

7. (4)

When two bulbs are connected in series, the resistance of the circuit increases and so the voltages in each decreases, hence the brightness and the temperature also decreases. Due to decrease in temperature, the resistance of the carbon filament will slightly increase while that of metal filament will decrease. Hence, carbon filament will glow more brightly. Also, carbon is not a semiconductor.

### Case-Study Based MCQ

1. Read the following passage and answer carefully.

The resistance of a conductor depends on its length L and area of cross section A. It also depends in the nature of the material and temperature. If the temperature is kept constant, the resistance of a conductor depends on its length L and area of cross section A. It also depends on the nature of the material and temperature. If the temperature is kept constant, the resistance of a conductor is directly proportional to its length and inversely to its area of cross section.

As temperature is increased, the resistivity of of a conductor will also increase. But it is not a linear relationship. In SI unit, resistance is expressed in ohm and resistivity in ohm-metre.

(i) A cylindrical wire has a resistance of 18ohm. The resistance of another wire of the same material with the same cross section, but 1.5 times the length is

(a) 18 ohm
(b) 27 ohm
(c) 12 ohm
(d) 9 ohm

(ii) If a cuboidal conductor is as follows, then its resistance is the most between which pair of points?

P and Q are the centres of top and bottom surfaces, A and B are those of longer sides and C and D are centres of shorter sides.

(a) AB
(b) CD
(c) PQ
(d) All have the same resistance

(iii) R is the resistance of a cylindrical wire. If it is stretched to twice of it length, keeping the volume constant, the new resistance will be

(a) R
(b) 2R
(c) 4R
(d) R/2

(iv) In an experiment, a sample of wire has a resistance 20 ohm at 15 degree celcius. If the experiment is conducted keeping the same wire sample at a temperature of 30 degree celcius, then the possible value of its resistance can be

(a) 20 ohm
(b) 10 ohm
(c) 15 ohm
(d) 22.5 ohm

2. Read the following passage and answer accordingly.

When an inductor is connected to a source of emf and the switch is closed, initially the inductor offers infinite reactance to the current. As a result, first after closing the switch, the current in the circuit will be zero.

But as time passes, the reactance reduces and after a long time the current through the inductor will be maximum.

Switch S is closed at t=0. Just after switch is closed

(i) which point is at higher potential?

(a) 1
(b) 2
(c) both are at same potential
(d) none of these

(ii) The potential difference V12 across R1 is

(a) 75 V
(b) 125 V
(c) 150 V
(d) 112.5 V

(iii) The potential difference V34 across L is

(a) 75 V
(b) 125 V
(c) 150 V
(d) 112.5 V

(iv) Which point is at lighter potential?

(a) 3
(b) 4
(c) both
(d) none

### Case-Study Based MCQ Answers

1. (i)(b) (ii)(b) (iii)(c) (iv)(d)

2. (i)(a) (ii)(c) (iii)(c) (iv)(b)

Click Below To Learn Chemistry Term-1 Syllabus Chapters MCQs

Final Words

From the above article, you have practiced Current Electricity MCQ of Class 12 Physics Chapter 3. We hope that the above mentioned latest MCQs for Term 1 of Chapter 3 Current Electricity will surely help you in your exam.

If you have any doubts or queries regarding the Current Electricity MCQ with Answers of CBSE Class 12 Physics, feel free to reach us and we will get back to you as early as possible.

Click Below To Learn
Physical Education Term-1 Syllabus Chapters MCQ

Share on:
error: Content is protected !!