Grade 11 Electrostatics Chapter Electric Charge Practice Questions

                                              Electric Charge

Multiple Choice Questions:

1. In order to remove static electricity from machinery

(a) construct insulated cabins

(b) insulate the machinery

(c) ground the framework

(d) humidify the surroundings

Ans: c

2. If a third equal and similar charge is placed between two equal and similar charges, then this third charge will

(a) move out of the field of influence of the two charges

(b) remain in stable equilibrium

(c) not be in equilibrium

(d) be in unstable equilibrium

Ans: b

3. A region around a stationary electric charge has

(a) an electric field

(b) a magnetic field

(c) both (a) and (b)

(d) none of the above

Ans: a

4. The minimum value of potential gradient in a cable occurs in

(a) insulation

(b) conductor

(c) outer sheath

(d) uniformly all over

Ans: a

5. Dielectric strength of medium

(a) increases with rise in temperature

(b) increases with moisture content

(c) is same for all insulating materials

(d) none of the above

Ans: d

6. A charge which when placed in vacuum from an equal and similar charge repels with a force of 9 x 10 N, is known as

(a) milli-coulomb

(b) micro-coulomb

(c) pico-coulomb

(d) coulomb

Ans: b

8. Dielectric strength of a medium is usually expressed in

(a) J/mm

(b) C/m2

(c) kV/mm

(d) N/mm

Ans: c

9 . A positive and a negative charge are initially 50 mm apart. When they are moved close together so that they are now only 10 mm apart, the force between them will be

(a) 5 times smaller than before

(b) 5 times greater than before

(c) 10 times greater than before

(d) 25 times larger than before

Ans: d

10. Which is the most superior dielectric out of the following ?

(a) Air

(b) Glass

(c) Bakelite

(d) Paper

Ans: c

11. When a dielectric is placed in an electric field the field strength

(a) decreases

(b) increases

(c) reduces to zero

(d) remain unchanged

Ans: a

136. To prevent the generation of static charges on rubber or flatleather

(a) surface is moistened

(b) conductive dressing is done

(c) oil compound dressing is done

(d) talcum powder is sprayed on the surface

Ans: b

  Short Questions:

1. Can a charged body attract an uncharged body ? Explain.

2. What do you mean by quantization of charge?

3. Why are sharp edges or points avoided in electrical machines?

4. What is electrostatic shielding?

  5. A man inside the insulated metallic case does not receive shock when the case is highly charged. Why?

6. The vehicle carrying inflammable fluid drag a chain along the ground. Why?

Numericals:

1. Determine the electrostatic force of interaction between the electron and nucleus in a hydrogen atom. The mean distance of electron from the nucleus of the atom is 1 x 10^-10 m .

2. A polythene piece rubbed with wool is found negatively charge of 3 x 10^-7 C. Estimate the number of  electrons transferred from wool to polythene.

3. Two equal and similar charges are 3 cm apart in air repel each other a force of  4.5 Kg wt. Find the charge in Coulomb.

4. An alpha particle is the nucleus of helium atom. It has mass 6.64 x 10^-27 kg and charge q = 2e = 2 x 1.6 x 10^-19 C. Compare the electrostatic force and gravitational force between the two alpha particles.

5.Three charges of10 esu, -10 esu, and 5 esu are placed in air, At the corner A, B and C of an equilateral triangle ABC having each side 5 cm. Find the force acting on the smallest charge.