# Electric Charges And Fields – Multiple Choice Questions

Q1. Ratio of the permittivity of a medium to the permittivity of free space is known as

1. Dielectric medium
2. Dielectric ratio
3. Dielectric permittivity
4. Dielectric constant

Q2. An electric dipole consists of a positive and negative charge of 4 μC. Each placed at a distance of 5 mm. The dipole moment for the system is

1. 20 x 10-8 C-m
2. 2 x 10-9 C-m
3. 2 x 10-8 C-m
4. 1 x 10-8 C-m

Q3. Two point charges QA = 2 μC and QB = -2 μC are located 16 cm apart in vacuum. What is the electric field at the mid point O of the line AB joining the two charges?

1. E = 5.6 × 106 N/C along OB
2. E = 5.6 × 106 N/C along OA
3. E = 6.5 × 106 N/C along OB
4. E = 6.5 × 106 N/C along OA

Q4. A scientific instrument used to detect the charge on a body is known as:

1. Electrometer
2. Electroscope
3. Charge detector
4. Miller counter

Q5. The value of charge on a body which carries 30 excess electrons is

1. -4.8 × 10 -19 C
2. -4.8 × 10 -18 C
3. -48 × 10 -18 C
4. 4.8 × 10-18 C

Q6. Electric lines of force never intersect each other because

1. Lines of force always repel each other
2. Lines of force always attract each other
3. Point of intersection signifies two direction of electric field
4. From the point of intersection four tangent can be drawn which signifies four direction of field

Q7. A material in which electrons are loosely bound and can move freely at room temperature is called a/an

1. Insulator
2. Semiconductor
3. Superconductor
4. Conductor

Q8. Which of the following statement is true?

1. Electric field lines start from negative charge
2. Electric field lines intersect with each other.
3. Electric field lines for single positive charge are radiated inwards.
4. Electric field lines do not form closed loops.

Q9. If a body contains n1 electrons and n2 protons, the total amount of charge on the body is

1. (n2 – n1)e
2. (n2 + n1) e
3. (n2 /n1)e
4. (n2 x n1)e

Q10. Two identical metallic spheres, having unequal opposite charges are placed at a distance of 0.90 m apart. After bringing them in contact with each other, they are again placed at the same distance apart. Now, the force of repulsion between them is 0.025 N. Calculate the final charge on each of them.

1. 1.5 × 10 -6 C
2. 1.5 × 10 -7 C
3. 1.3 × 10 -6 C
4. 2.5 × 10 -8 C

Q11. Two point charges 2 μC and 8μC are placed 12 cm apart. The position of point from 2 μC charge, where the electric field intensity is zero is:

1. 8 cm
2. 2 cm
3. 12 cm
4. 4 cm

Q12. The unit of permittivity of free space is

1. C2/N-m2
2. C2/ (N-m)2
3. C/N-m
4. N-m2/C2

Q13. Two glass rods rubbed with silk are placed close to each other. They will

1. Repel each other
2. Attract each other
3. Neither repel nor attract
4. Cannot predict without knowing the amount of charge

Q14. The ratio of electric field due to an electric dipole at points situated at a distance r along its axial line and along its equatorial plane is

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

Q15. The dimensional formula of µ0 is

1. [M-1 L-3 T4 A2]
2. [M-1 L-2 T4 A]
3. [M L-3 T4 A2]
4. [M L-3 T4 A]

Q16. To make an uncharged object have a positive charge:

1. Remove some electrons from it
2. Add some electrons to it
3. Remove some neutrons from it
4. Add some neutrons to it

Q17. The force between two small charged spheres having charges 3 × 10-6 C and 4 × 10-6 C placed 40 cm apart in air is

1. 6.75 × 10-1 N
2. 67.5 × 10-1 N
3. 6.75 × 10-2 N
4. 67.5 × 10-3 N

Q18. A charged comb attracts pieces of paper. Why does this happen?

1. paper also gets charged.
2. paper is polarized.
3. paper has no charge.
4. none of these.

Q19. Quantisation of charge means that

1. the charge on a body is a fraction of electronic charge, e
2. the total charge on a body is always conserved
3. the net charge on a body is always zero
4. The charge on a body is an integral multiple of electronic charge, e

Q20. The field lines for single positive charge are:

2. Parallel
3. Circular

Q21. A silk cloth rubbed with a glass rod acquires a charge (-1.6 × 10-19 C). Then the charge on the glass rod is

1. – 1.6 × 10 -19 C
2. +1.6 × 10 -19 C
3. – 3.2 × 10 -19 C
4. 3.2 × 10 -19 C

Q22. What is the angle between the electric dipole moment and the electric field on the equatorial line of the dipole?

1. 90°
2. 180°
3. none of the above

Q23. When a charged rod is brought near the disc of a negatively charged gold leaf electroscope, it is observed that the divergence of leaves decreases.  What reference do you draw about the charge on the rod?

1. Rod is positively charged
2. Rod is negatively charged
3. Rod has no charge
4. None of the above

Q24. Electric flux through a surface does not mean a flow of electric charges through it.

1. True
2. False
3. Depends on the surface
4. Depends on the charge

Q25. If an excess charge is placed on an isolated conductor, then, that amount of charge

1. gets neutralized.
2. resides on the surface of conductor.
3. move inside the conductor.
4. either resides on the surface of conductor or gets neutralized.

Q26. A dipole is said to be in unstable equilibrium when angle between electric field and dipole moment is.

1. 45°
2. 90°
3. 180°

Q27. For uniform electric field, field lines are:

1. Divergent
2. Convergent
3. Convergent then divergent
4. Parallel and equally spaced

Q28. A test charge of 3nC is placed at origin and experiences a force of 9 x 10-4 N. The electric field at origin is:

1. 9 x 105 N/C
2. 3 x 105 N/C
3. 0.3 x 105 N/C
4. 1 x 105 N/C

Q29. Two point charges +4 μC and +6 μC repel each other with a force of 12 N. If each of them is given an additional charge -5 μC, what will be the new force between them?

1. 1 N
2. 3 N
3. 5 N
4. 2 N

Q30. A material in which electrons are tightly bound and cannot move freely at room temperature is called a/an

1. Insulator
2. Semiconductor
3. Superconductor
4. Conductor

Q31. What will be the magnitude of dipole moment for two charges ±10 nC separated by 10 mm?

1. 2 Cm
2. 10-10 Cm
3. 2 × 10-10 Cm
4. 20 Cm

Q32. The S.I unit of electric flux is:

1. N/m2C
2.  Nm2 /C
3. m2C/N
4. NC/m2

Q33. ‘A force on any charge due to a number of other charges is the vector sum of all the forces on that charge due to other charges’ is the statement of

1. Principle of Coulomb
2. Principle of conservation of charge
3. Principle of superposition
4. Principle of conservation of force

Q34. Which among the following is false for induction?

• (a) The process of induction happens instantly.
• (b) After induction, charges move towards the center of the conductor.
1. Only a
2. Only b
3. Both a and b are false
4. Neither a nor b is false

Q35. Which of the following quantities is a vector?

1. Electric flux
2. Electric potential
3. Electric potential energy
4. Electric field intensity

Q36. Choose the correct statement from the following

1. The total positive charge of the universe is constant
2. The total negative charge of the universe is constant
3. The total charge of the universe is constant
4. The total number of charged particles in the universe remains constant

Q37. Trajectory of an electron when it moves perpendicular to the electric field is

1. Parabolic
2. Circular
3. Straight
4. Hyperbolic

Q38. To make an uncharged object have a negative charge:

1. Remove some electrons from it
2. Add some electrons to it
3. Add some neutrons to it
4. Remove some neutrons from it

Q39. The dipole moment of a system consisting of a proton and an electron separated by 4 nm is

1. 3.2 × 10−28 Cm
2. 12.8 × 10−28 Cm
3. 19.2 × 10−28 Cm
4. 6.4 × 10−28 Cm

Q40. At what point is the electric field intensity due to a uniformly charged spherical shell maximum?

1. inside the spherical shell
2. outside the spherical shell
3. at the surface of a spherical shell
4. at the center of the spherical shell