Practice Electrostatics Questions and Answers

**Electrostatics Questions and Answers**

**Q1. Two point charges +q _{1} and +q_{2} are fixed with a finite distance ‘d’ between them. It is desired to put a third charge q_{3} in between these two charges on the line joining them so that the charge q_{3} is in equilibrium . That is : **

*(a) Possible only if q*_{3}is positive*(b) Possible only if q*_{3}is negative*(c) Possible irrespective of the sign of q*_{3}*(d) Not possible at all*

**Q2. Five negative electric charges of magnitude e are placed symmetrically on a circle of radius R. The magnitude of the electric field at the center of the circle is **

*(a)*^{e}/_{4πεoR2}*(b) 0**(c)*^{e}/_{4πεoR2}sin^{2π}/_{5}*(d)*^{5e}/_{4πεoR2}

*Q3. A thin spherical oil drop carrying a net charge q is balanced in still air with a vertical uniform electric field of strength ^{81}/_{7} × 10^{5} Vm^{-1} . When the field is switched off the drop is observed to fall with terminal velocity 2 × 10^{-3} ms^{-1} . Given, g = 9.8 m/s^{2}, viscosity of the air = 1.8 × 10^{-5} Ns/m^{2} and the density of oil = 900 kg m^{-3}, the magnitude of q is *

*(a) 1.6 × 10*^{-19}C*(b) 3.2 × 10*^{-19}C*(c) 4.8 × 10*^{-19}C*(d) 8.0 × 10*^{-19}C

**Q4. A charge q is at the center of two concentric spheres. The outward electric flux through the inner sphere is φ while that through the outer sphere is 2φ. The amount of charge contained in the region between the two spheres is **

*(a) 2q**(b) q**(c) -q**(d) -2q*

**Q5. A sphere of radius R and a uniform total Charge Q is centered at origin, total electric flux through a Gaussian sphere of radius R centered at (0,0,d) is**

*(a) zero if d > 2R**(b)*^{Q}/_{εo}if d = 0*(c)*^{Q}/_{2εo}if d = R*(d)*^{Q}/_{2εo}if d < R

**Q6. If the electric flux through a closed surface S is equal to zero, then**

*(a) the volume charge density is zero everywhere inside the surface S**(b) the electric field at every point on S is zero.**(c) the electric field is zero at every point inside S**(d) the net charge enclosed by S is zero*

**Q7. Electric Potential in a particular region of space is V = 5x – 3x²y + 2yz². The magnitude of electric field at point P(m,0,-2m) is **

*(a) 5 N/C**(b) 6 N/C**(c) 7.08 N/C**(d) 9.0 N/C*

**Q8. A uniform electric field pointing in positive x-direction exists in a region. Let A be the origin, B be the point on x-axis at x = +1 cm and C be the point on the y-axis at y = +1 cm. Then the potentials at the points A, B and C Satisfy**

*(a) V*_{A}< V_{B}*(b) V*_{A}> V_{B}*(c) V*_{A}< V_{C}*(d) V*_{A}> V_{C}

*Q9. Electric potential in region is V(r) = Ar ^{3} + B . Charge enclosed by a sphere of radius R is centered at origin is Q_{o} . Charged enclosed by concentric sphere of radius 2R is *

*(a) Q*_{o}*(b) 4Q*_{o}*(c) 16Q*_{o}*(d) 32Q*_{o}

*Q10. A ring of radius R has charge density +λ on one half and -λ on the other half. Its dipole moment is *

*(a) 4λR²**(b) 2λR²**(c) 3λR²**(d) λR²*

**Q11. Two point charges q and -2q lie at x = -a and x = +a respectively. Which of the following statements is/are correct **

*(a) There is only one neutral point on x-y plane**(b) At large distance r>>a*^{E(r)}/_{E(2r)}= 4*(c) Equipotential lines on x-y plane are circles**(d) Electric flux through y-z plane is*^{3q}/_{2εo}

**Q12. Three concentric metallic spherical shells of radii R, 2R, 3R are given charges Q _{1}, Q_{2}, Q_{3} respectively. It is found that the surface charge densities on the outer surface of the shells are equal. Then, the ratio of the charges given to the shells Q_{1} : Q_{2} : Q_{3} is**

*(a)*1 : 2 : 3*(b)*1 : 3 : 5*(c)*1 : 4 : 9*(d)*1 : 8 : 18

**Q13. A steady current in a straight conducting wires produces a surface charge on it. Let E _{out} and E_{in} be the magnitudes of the electric fields just outside and just inside respectively. Which of the following statements is true for these fields ?**

*(a) E*_{out}is always greater than E_{in}*(b)**E*_{out}is always smaller than E_{in}*(c)**E*_{out}could be greater or smaller than E_{in}*(d) E*_{out}is equal to E_{in}

*Q14. A charge q is placed at the centre of an otherwise neutral dielectric sphere of radius ‘a’ and relative permittivity ε _{r} . We denote the expression ^{q}/_{4πεor²} by E(r). Which of the following statement is false ?*

*(a) The electric field inside the sphere, r<a, is given by E(r)**(b) The field Outside the sphere, r>a, is given by E(r)**(c) The total charge inside a sphere of radius r>a is given by q.**(d) The total charge outside a sphere of radius r<a is given by q.*

**Q15. A bound volume charge density inside the sphere at a distance r from the centre is :**

*(a) -4kR**(b) -4kr**(c) -4kr²**(d) -4kr*^{3}

NOTE:- If you need anything else like e-books, video lectures, syllabus, etc. regarding your Preparation / Examination then do 📌 mention it in the Comment Section below. |

**Answer Key** (if you find any answer wrong, feel free to Correct us)

**Answer Key**(if you find any answer wrong, feel free to Correct us)

01. | (b) | 06. | (d) | 11. | (a), (b), (d) |

02. | (b) | 07. | (c) | 12. | (b) |

03. | (b) | 08. | (b) | 13. | (a) |

04. | (c) | 09. | (c) | 14. | (d) |

05. | (a), (b) | 10. | (a) | 15. | (b) |