Electric Charges And Fields Mock Test

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Quiz: Electric Charges and Fields Online Test (Progressive Test)
Total questions: 484
Questions in this round: 50
Time allotted: 70 minutes
Pass score: 60%
Total rounds: 10
Current round: 1^st
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Quiz: Electric Charges and Fields Online Test (Certificate Challenge)
Total questions: 484
Questions to attempt: 100 random
Time allotted: 100 minutes
Certificate pass score: 70%
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Progressive Test — Guest First Round

Class 12 Physics: Electric Charges and Fields Online Test

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1 / 50

1. Two identical conducting spheres are isolated from surroundings. Sphere P has charge , and sphere Q is neutral. They touch and are then separated. The charge on each sphere after separation is

2 / 50

2. A spherical shell, an infinite line charge, and an infinite plane sheet are used in three Gauss-law derivations. The common reason Gauss’s law becomes directly useful in all three is that

a) every Gaussian surface encloses zero charge

b) the electric field is always constant everywhere in space

c) all three charge distributions produce the same distance dependence

d) symmetry simplifies on the Gaussian surface

3 / 50

3. Use the arrangement described below.

A positive point charge, an infinitely long positive line charge, and an infinite positive plane sheet are considered separately. At a chosen distance , their field magnitudes are adjusted to be equal. The observation point is then moved farther away to from each source.

After moving the point to , the largest field belongs to the

a) all three remain equal

b) point charge

c) infinitely long line charge

d) infinite plane sheet

4 / 50

4. Assertion: The electric field at a point can be zero even when the point is near more than one charge.
Reason: Electric field is a vector quantity, so equal and opposite field contributions can cancel.

a) Both Assertion and Reason are true, but Reason does not explain Assertion

b) Assertion is true, but Reason is false

c) Both Assertion and Reason are true, and Reason explains Assertion

d) Assertion is false, but Reason is true

5 / 50

5. Read the situation and answer the question.

A neutral aluminium sphere is kept on an insulating stand. A positively charged rod is brought close to the left side of the sphere without touching it. After a short time, charges inside the sphere have redistributed, but the sphere is still isolated from the ground.

What is the net charge of the sphere at this stage?

a) Negative

b) Zero

c) Alternating between positive and negative

d) Positive

6 / 50

6. Two equal-magnitude electrostatic forces act on a charge at right angles to each other. The magnitude of the resultant force is

7 / 50

7. The order of operations matters in induction. For a conductor to be left charged using a nearby positive rod, the suitable sequence is

a) remove the rod first, then bring earth near without connecting it

b) earth the conductor after the rod has already been removed

c) bring the rod near, earth it, remove earth, then remove the rod

d) touch the conductor with the positive rod, then rub it with silk

8 / 50

8. A student compares , , and for a Gaussian surface. The correct statement is

a) net flux depends on outside charge but not inside charge

b) if net flux is zero, electric field must be zero at every point on the surface

c) net flux depends on , while outside charges can affect local field

d) local field on the surface depends only on enclosed charge and never on outside charges

9 / 50

9. In the relation for an infinite line charge, the absence of in the final answer occurs because

a) the line charge has no charge over length

b) the electric field is zero at all distances

c) the Gaussian surface is not closed

d) cancels from both sides

10 / 50

10. A long charged wire and a point charge are adjusted so that their electric fields have the same magnitude at distance . If the distance from each source is changed to , then

a) both fields become zero

b) both fields remain equal

c) the point-charge field becomes larger than the wire field

d) the wire field becomes larger than the point-charge field

11 / 50

11. At the centre of a square, a charge experiences forces due to four corner charges. The two charges at one diagonal are and , while the two charges at the other diagonal are and . The net force on is

a) perpendicular to the plane of the square

b) along the diagonal joining the negative charges

c) along the diagonal joining the positive charges

d) zero

12 / 50

12. A closed surface encloses no charge, but an external charge produces a non-zero electric field at many points on the surface. The correct conclusion is that

a) the Gaussian surface cannot be used

b) the net flux must be

c) the electric field must be zero at every point of the surface

d) net flux is zero, but local flux may be non-zero

13 / 50

13. Near a positively charged conductor surface, the electric field just outside is directed

a) along the surface only where is large

b) tangential to the surface

c) outward normal to the surface

d) inward normal to the surface

14 / 50

14. A thin spherical shell of radius carries charge . A point is at , and a point is at , both measured from the centre. The ratio is

15 / 50

15. A graph of versus for a uniformly charged thin spherical shell of radius is compared with a graph for an infinite line charge. The correct comparison is

a) shell: for ; line:

b) shell: outside; line:

c) shell: for ; line:

d) shell: inside , outside ; line:

16 / 50

16. A uniformly charged conducting spherical shell is in electrostatic equilibrium. The charge resides on the outer surface mainly because

a) electric charge cannot exist on curved surfaces

b) Gauss’s law is invalid inside conductors

c) the inner region must contain equal positive and negative point charges

d) charge redistributes until the field inside the conductor is zero

17 / 50

17. A charge is placed exactly midway between two identical charges fixed on its left and right at equal distances. The net force on the middle charge is

a) vertically upward

b) zero

c) toward the left

d) toward the right

18 / 50

18. A closed surface contains a charge , and a charge is placed outside it. The net flux through the closed surface is

19 / 50

19. Two statements are made about conductors and insulators.
I. Charge can redistribute easily inside a conductor because some charge carriers are mobile.
II. An insulator contains no positive or negative charges inside its atoms.
III. A neutral conductor near a charged body may become polarized even when its net charge remains zero.
The supported statements are

a) I and II only

b) I, II and III

c) I and III only

d) II and III only

20 / 50

20. A uniformly charged infinite line has linear charge density . The electric field at distance from the line is directed

a) tangentially around the line in circles

b) along the length of the line for both signs of

c) zero at every point outside the line

d) outward for , inward for

21 / 50

21. Study the Gauss-law table and identify the row that is incorrect.

Row	Situation	Net flux through closed surface
P	Encloses
Q	Encloses
R	Encloses and
S	Encloses no charge but has outside charges nearby

a) Row P

b) Row Q

c) Row R

d) Row S

22 / 50

22. A charge placed at a point experiences a force of magnitude . The electric field magnitude at the point is

23 / 50

23. A body becomes negatively charged after receiving electrons from another body. Conservation of charge requires that the other body

a) creates negative charge inside itself

b) loses electrons and becomes relatively positive

c) also gains the same number of electrons

d) loses protons and becomes neutral in every case

24 / 50

24. The electric field outside a positively charged spherical shell varies with distance from its centre as

b) is independent of

25 / 50

25. For a curved surface in a non-uniform electric field, the electric flux is written as

26 / 50

26. A cube of side is kept in a uniform electric field . The outward normal of the right face is , and the outward normal of the left face is . The flux through the right face and left face respectively is

a) ,

b) ,

c) ,

d) ,

27 / 50

27. The torque on an electric dipole of moment placed in a uniform electric field is given by

28 / 50

28. The electric dipole consists of

a) two equal positive charges at the same point

b) equal opposite charges separated by distance

c) two unequal charges with no separation

d) one isolated positive charge only

29 / 50

29. Study the field-line descriptions and identify the one that is not acceptable for an electrostatic field.

Row	Description
P	Lines are closer where the field is stronger.
Q	The tangent to a line gives the direction of .
R	Two field lines cross where the field is very strong.
S	Lines start from positive charge and end on negative charge.

a) Row P

b) Row S

c) Row R

d) Row Q

30 / 50

30. A negatively charged rod is brought near, but does not touch, a neutral metal sphere on an insulating stand. The near side of the sphere becomes relatively positive. This happens because

a) protons move freely to the near side through the metal

b) electrons in the sphere are repelled toward the far side

c) the rod becomes neutral as soon as it is brought near

d) the sphere gains net positive charge from the rod

31 / 50

31. Once Gauss’s law gives for a point charge , the force on a test charge placed at that distance is

32 / 50

32. Assertion: In standard charging by induction, the final charge on the conductor is opposite in sign to the inducing charge.
Reason: During the earthing step, electrons move in a direction decided by the inducing charge, while the inducing body does not touch the conductor.

a) Assertion is false, but Reason is true

b) Both Assertion and Reason are true, and Reason explains Assertion

c) Both Assertion and Reason are true, but Reason does not explain Assertion

d) Assertion is true, but Reason is false

33 / 50

33. A dipole of moment is in a uniform electric field . At an angle , its torque magnitude is and potential energy is . If and , then equals

34 / 50

34. Assertion: At the same far distance from a dipole, the axial field is twice the equatorial field in magnitude.
Reason: The far axial field is proportional to , while the far equatorial field is proportional to .

a) Assertion is false, but Reason is true

b) Both Assertion and Reason are true, and Reason explains Assertion

c) Both Assertion and Reason are true, but Reason does not explain Assertion

d) Assertion is true, but Reason is false

35 / 50

35. An isolated oil drop has charge . Taking , the value of in is

36 / 50

36. A flat insulating sheet carries charge uniformly over its surface. The most suitable density symbol for describing this distribution is

37 / 50

37. In deriving the axial field of a dipole, the subtraction of two field magnitudes occurs because

a) the two axial fields are oppositely directed

b) the axial point is always exactly at the centre

c) the two charges have equal signs

d) electric field is a scalar quantity

38 / 50

38. A far dipole field is compared with the field of a single point charge. The dipole field decreases faster with distance because it varies as

a) , while a point-charge field varies as

b) , while a point-charge field varies as

c) , while a point-charge field varies as

d) , while a point-charge field varies as

39 / 50

39. A dipole has charges separated by . The exact axial field at distance from the centre is . For , this exact field becomes

40 / 50

40. A positive charge and another positive charge are fixed on a straight line. The electrostatic force on each charge acts

a) in the same direction on both charges

b) perpendicular to the line joining them

c) along the line, away from each other

d) only on the smaller charge

41 / 50

41. A conductor is polarized by a nearby charged rod, but the rod is removed before the conductor is earthed. The conductor is least likely to remain charged because

a) the conductor loses all electrons permanently during polarization

b) polarization fades before charge is trapped

c) earthing always creates charge on any conductor even without a nearby rod

d) the conductor becomes an insulator as soon as the rod is removed

42 / 50

42. A charge is placed at the centre of a spherical Gaussian surface of radius . The electric flux through the sphere is

43 / 50

43. A force calculation table is prepared for a charge under the influence of two other charges.

Row	Statement
P	The force due to each source charge is calculated separately.
Q	The net force is the vector sum of individual forces.
R	Forces in opposite directions must be subtracted algebraically after choosing an axis.
S	The net force is always the arithmetic sum of magnitudes, regardless of direction.

The row that needs correction is

a) Row P

b) Row R

c) Row Q

d) Row S

44 / 50

44. A student writes . This value represents

a) the linear charge density of a wire

b) the elementary charge

c) the Coulomb force between unit charges

d) the vacuum permittivity

45 / 50

45. Two charges and are fixed on a line. At any point between them, the electric field contributions due to the two charges are

a) in the same direction

b) in opposite directions

c) perpendicular to the line joining the charges

d) always zero separately

46 / 50

46. A plane surface has its area vector directed opposite to a uniform electric field. The electric flux through the surface is

47 / 50

47. A graph has three labelled curves for electric field magnitude against distance . Curve P falls as , curve Q falls as , and curve R is horizontal. The most suitable source matching is

a) P: point charge, Q: infinite line charge, R: infinite plane sheet

b) P: infinite plane sheet, Q: point charge, R: infinite line charge

c) P: infinite line charge, Q: infinite plane sheet, R: point charge

d) P: conductor interior, Q: point charge, R: spherical shell interior

48 / 50

48. A charge list is written as , , , and . The net charge in terms of is

49 / 50

49. A charged conducting sphere of radius has surface charge density . The electric field just outside its surface is compared with the electric field at distance from its centre. The ratio is

50 / 50

50. A point charge is kept at the centre of a spherical Gaussian surface. The field is first found from Gauss’s law and then a charge is placed on the surface. The force on is

a) away from the centre with magnitude

b) tangential to the spherical surface

c) zero because Gauss’s law gives only flux

d) toward the centre with magnitude

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Electric Charges and Fields Mock Test – Class 12 Physics

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Class 12 Physics: Electric Charges and Fields Online Test

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