12 - Physics - Unit 1 - Electro Statics
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The electrostatic force between two point charges kept at a distance d apart, in a medium εr = 6, is 0.3 N. The force between them at the same separation in vacuum is
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1.8 N
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0.5 N
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20 N
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2 N
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- 2.
Elecric field intensity is 400 V m−1 at a distance of 2 m from a point charge. It will be 100 V m−1 at a distance?
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4 m
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4 cm
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1.5 m
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50 cm
Correct Answer
A. 4 mExplanation
The electric field intensity decreases with distance from a point charge. Since the electric field intensity is 400 V m−1 at a distance of 2 m, it will be 100 V m−1 at a distance that is 4 times greater, which is 4 m.Rate this question:
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- 3.
Two point charges +4q and +q are placed 30 cm apart. At what point on the line joining them the electric field is zero?
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20 cm from the charge 4q
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15 cm from the charge q
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7.5 cm from the charge q
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5 cm from the charge q
Correct Answer
A. 20 cm from the charge 4qExplanation
The electric field at a point on the line joining two charges is zero when the magnitudes of the electric fields produced by the charges at that point are equal and opposite. In this case, the charge +4q produces an electric field that is four times stronger than the electric field produced by the charge +q. To balance out the stronger electric field, the point where the electric field is zero must be closer to the charge +4q. Therefore, the correct answer is 20 cm from the charge 4q.Rate this question:
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- 4.
A dipole is placed in a uniform electric field with its axis parallel to the field. It experiences
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Neither a net force nor a torque
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Only a torque
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Both a net force and torque
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Only a net force
Correct Answer
A. Neither a net force nor a torqueExplanation
When a dipole is placed in a uniform electric field with its axis parallel to the field, the positive and negative charges of the dipole experience equal and opposite forces. These forces cancel each other out, resulting in no net force on the dipole. Additionally, since the forces on the positive and negative charges are equal in magnitude and opposite in direction, they also create equal and opposite torques. These torques also cancel each other out, resulting in no net torque on the dipole. Therefore, the dipole experiences neither a net force nor a torque in this situation.Rate this question:
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- 5.
The work done in moving 500 μC charge between two points on equipotential surface is
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Zero
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Finite positive
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Finite negative
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Infinite
Correct Answer
A. ZeroExplanation
The work done in moving a charge between two points on an equipotential surface is zero because the potential difference between any two points on an equipotential surface is zero. This means that the electric field is perpendicular to the equipotential surface, and therefore no work is done in moving the charge along that surface.Rate this question:
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- 6.
Which of the following quantities is scalar?
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Electric potential
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Electric force
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Electric field
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Dipole moment
Correct Answer
A. Electric potentialExplanation
Electric potential is a scalar quantity because it only has magnitude and no direction. It represents the amount of electric potential energy per unit charge at a given point in an electric field. Unlike electric force, electric field, and dipole moment, electric potential does not have a specific direction associated with it. Therefore, it is considered a scalar quantity.Rate this question:
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- 7.
The capacitance of a parallel plate capacitor increases from 5 μf to 60 μf when a dielectric is filled between the plates. The dielectric constant of the dielectric is
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12
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55
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65
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10
Correct Answer
A. 12 -
- 8.
A hollow metal ball carrying an electric charge produces no electric field at points
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Inside the sphere
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On its surface
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Outside the sphere
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At a distance more than twice
Correct Answer
A. Inside the sphereExplanation
A hollow metal ball carrying an electric charge produces no electric field at points inside the sphere because the electric field inside a conductor in electrostatic equilibrium is zero. The charges on the inner surface of the hollow sphere redistribute themselves in such a way that the electric field due to them cancels out, resulting in no net electric field inside the sphere.Rate this question:
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- 9.
A glass rod rubbed with silk acquires a charge of . The number of electrons it has gained or lost (1) (gained) (2) (lost) (3) (lost) (4) (lost)
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(2)
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(1)
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(4)
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(3)
Correct Answer
A. (2)Explanation
When a glass rod is rubbed with silk, it acquires a positive charge. This means that it has lost electrons, as electrons are negatively charged particles. Therefore, the correct answer is (2) lost.Rate this question:
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- 10.
If a point lies at a distance x from the midpoint of the dipole, the electric potential at this point is proportional to (1) (2) (3) (4)
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(1)
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(2)
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(3)
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(4)
Correct Answer
A. (1)Explanation
The electric potential at a point due to a dipole is inversely proportional to the distance from the midpoint of the dipole. Therefore, if a point lies at a distance x from the midpoint of the dipole, the electric potential at this point is proportional to 1/x. Hence, the correct answer is (1).Rate this question:
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- 11.
Four charges +q, +q, −q and –q respectively are placed at the corners A, B, C and D of a square of side a. The electric potential at the center O of the square is (1) (2) (3) (4) zero
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(4)
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(3)
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(2)
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(1)
Correct Answer
A. (4)Explanation
The electric potential at the center O of the square is zero because the charges at corners A and C are equal in magnitude but opposite in sign, canceling out each other's electric potential. The same is true for the charges at corners B and D. Therefore, the net electric potential at the center O is zero.Rate this question:
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- 12.
Electric potential energy (U) of two point charges is (1) (2) (3) pE cos θ (4) pE sin θ
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(2)
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(3)
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(1)
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(4)
Correct Answer
A. (2)Explanation
The correct answer is (2) because the electric potential energy (U) of two point charges is given by the formula U = k(q1*q2)/r, where k is the electrostatic constant, q1 and q2 are the magnitudes of the charges, and r is the distance between the charges. The given option (2) matches this formula, indicating that it is the correct answer.Rate this question:
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- 13.
The unit of permittivity is (1) C2 N−1 m−2 (2) N m2 C−2 (3) H m−1 (4) N C−2 m−2
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(1)
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(2)
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(3)
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(4)
Correct Answer
A. (1)Explanation
The unit of permittivity is given by C2 N−1 m−2. This unit represents the amount of electric charge (Coulombs) per unit area (m2) required to produce a unit electric field (N). Therefore, option (1) is the correct answer.Rate this question:
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- 14.
The number of electric lines of force originating from a charge of 1 C is (1) (2) (3) (4)
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(1)
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(2)
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(3)
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(4)
Correct Answer
A. (1)Explanation
The number of electric lines of force originating from a charge of 1 C is directly proportional to the magnitude of the charge. Since the charge is given as 1 C, there will be a single electric line of force originating from it.Rate this question:
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- 15.
The electric field outside the plates of two oppositely charged plane sheets of charge density σ is (1) (2) (3) (4) zero
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(4)
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(3)
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(2)
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(1)
Correct Answer
A. (4)Explanation
The electric field outside the plates of two oppositely charged plane sheets of charge density σ is zero. This is because the electric field created by one sheet cancels out the electric field created by the other sheet due to their opposite charges. Therefore, outside the plates, the net electric field is zero.Rate this question:
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Nov 29, 2013Quiz Created by
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