WBCHSE Class 12 Physics Notes For Elementary Phenomena Of Electrostatics Question and Answers

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Exercise Multiple Choice Question And Answer

Question 1. A positively charged glass rod attracts a light-hanging body and thereafter repels it. The hanging body initially was

1. Positively charged
2. Earth-connected
3. Negatively charged
4. Uncharged

Answer: 3. Negatively charged

Question 2. Five balls marked by numbers from 1 to 5 are hung by different threads. It is seen that the pairs of balls (1,2), (2,4), and (4,1) attract each other. Again the pairs (2, 3) and (4, 5) repel each other. So the ball marked by 1 is

1. Positively charged
2. Negatively charged
3. Uncharged
4. Made by metal

Answer: 3. Uncharged

Question 3. The charges of the clouds responsible for lightning are produced due to

1. Conversion of raindrops into elections
2. The electric field of the earth
3. Creation of ions by the sun
4. Friction among the water drops.

Answer: 4. Friction among the water drops

Question 4. 106 electrons are given to a pith ball. The charge of the ball will be

1. 1.6 x 10^-13 C
2. 1.6 X 10^-25 C
3. 1.6 x 10^-19 C
4. None of the above

Answer: 3. 1.6 x 10^-19C

Question 5. A glass rod rubbed with silk becomes positively charged because

1. Protons are added to the glass rod
2. Protons are removed from the glass rod
3. Electrons are added to the glass rod
4. Electrons are removed from the glass rod

Answer: 4. Electrons are removed from the glass rod

Question 6. Two identical metallic spheres of the same mass are taken. Positive Q C charge is developed on one and an equal amount of negative charge is developed on the other. After charging

1. The two spheres will have equal mass
2. The sphere charged negatively will have a greater mass
3. The sphere charged positively will have a greater mass
4. The sphere charged negatively will have a smaller mass

Answer: 2. The sphere charged negatively will have a greater mass

Question 7. If a body is charged by rubbing, its weight

1. Does not change
2. Increases a little
3. Decreases a little
4. May increase or decrease a little

Answer: 4. May increase or decrease a little

Question 8. If the charge of an electron is 1.6 x 10^-19 C, which one of the following cannot be the charge of a body?

1. 3.2 x 10^-10 C
2. 4.8 x 10^-10 C
3. 5.6 x 10^-19 C
4. 1.6 x 10^-19 C

Answer: 3. 5.6 x 10^-19 C

Question 9. Electrostatic induction can be brought about

1. In conductors only
2. In insulators only
3. In bad conductors only
4. In both conductors and insulators

Answer: 4. In both conductors and insulators

Question 10. Two charged spheres attract each other with a force. They are touched by each other and thereafter brought back to their initial positions, the two spheres

1. Attract each other with a smaller force
2. Attract each other with a greater force
3. Repel each other with a smaller force
4. Repel each other with a greater force

Answer: 3. Repel each other with a smaller force

Question 11. The charge of a conductor resides on its outer surface of This statement is correct

1. In all cases
2. In the case of solid and hollow conductors
3. In the case of only spherical conductors
4. In the case of the conductors having no pointed ends

Answer: 1. In all cases

Question 12. With respect to a hollow sphere, a solid metallic sphere of the same radius will retain

1. More charge
2. Less charge
3. An equal amount of charge
4. None of the above

Answer: 3. Equal amount of charge

Question 13. The unit of surface density of charge in SI is

1. C
2. C m^-1
3. C.m^-2
4. C.m^-3

Answer: 3. C.m^-2

Question 14. The diameter of a hollow conducting sphere is 2 cm. The sphere has a 12.56 unit charge, the surface density of charge in its inner surface in CGS units

1. 0
2. 1
3. 12.56
4. 6.28

Answer: 1. 0

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Very ShortAnswer Type Questions

Question 1. If a glass rod is rubbed with silk, what kind of charge is produced on the rod?
Answer: Positive

Question 2. If an ebonite rod is rubbed with flannel, what kind of charge is produced on the rod?
Answer: Negative

Question 3. A, B, and C are three charged bodies. If A and B repel each other and A attracts C, what will be the nature of the force acting between B and C?
Answer: Attractive

Question 4. Two point charges qx and q2 are such that qxq2< 0. What is the nature of the force acting between the two
Answer: Attractive

Question 5. What is the number of electrons in a 1C charge?
Answer: 6.25 x 10¹⁸

Question 6. If a body has a 1.5 x 107 number of excess electrons, what is the charge on the body?
Answer: -2.4 x 10^-12C

Question 7. If 1022 electrons are transferred from a metallic sphere, what will be the charge of the sphere?
Answer: 1600 C positive charge

Question 8. Write the name of a good conductor.
Answer: Silver

Question 9. Write the name of an insulator.
Answer: Glass

Question 10. What kind of charges are produced at the near end and at the far end of a conductor due to induction?
Answer: Opposite, similar

Question 11. Which is the appropriate season for performing experiments on statical electricity?
Answer: Winter

Question 12. Where does the charge of a conductor reside?
Answer: Outer surface

Question 13. What should be the shape of a conductor to retain its charge?
Answer: Spherical

Question 14. If a cubical conductor is charged, where will the surface density of charge be maximum?
Answer: At each of the vertices of the cube

Question 15. Is it safe or unsafe to remain inside a car at the time of
lightning?
Answer: Safe

Question 16. Why are two metal plates placed on the two inner sides of a gold-leaf electroscope?
Answer: To increase the divergence of the gold leaves

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Fill In The Blanks

1. Repulsion is the surer test of electrification.

2. In SI, the amount of charge of an electron is 1.6 x 10^-19C

3. The charge on an electron is the smallest magnitude of charge in nature.

4. Dry air is a good insulator

5. Diamonds, ebonite, and bakelite are non-conductors of electricity.

6. If complete induction takes place, the amount of the inducing charge and that of the induced charge become equal.

7. In the case of electrostatic induction there should be a gap between the charged body and the uncharged body.

8. Induction precedes attraction.

9. The greater the curvature of a region of a conductor, the greater the accumulation of charge at that region.

10. In the case of a spherical conductor, the surface density of charge is equal everywhere.

11. Charge resides only on the outer surface of a conductor.

12. Charging of a gold-leaf electroscope by the process of conduction is not a good process.

13. If the charge of an experimental body and that of a gold-leaf electroscope are of the same nature, the divergence of the leaves of the gold-leaf electroscope will increase

14. To determine the nature of the charge of a body it is brought slowly to a charged electroscope from a distance.

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Problem Set – 1

Question 1. A body has a -80μC charge. What is the number of excess electrons in the body?
Answer: 5 X 10¹⁴

Question 2. A conductor is clinked with 14.4 x 10¹⁹C. Determine the number of the deficit of electrons. In it, What will he the change In men of the conductor?
Answer: 9, 81 x 10^-13 kg mass (decrease)

Question 3. How much charge Is to be given to a sphere of radius 30cm so that its surface density of charge will be \(\frac{2}{\pi}\) CGS unit?
Answer: 7200 CGS unit

Question 4. The surface area of a body Is 25 cm2 and Its surface density of charge Is 5 CGS units. What Is the total charge on it?
Answer: 125 CGS unit

Question 5. What will be the surface density of charge of a sphere of radius 4 cm, If it is given 182 esu of charge?
Answer: 0.9 esu.cm^-2

Question 6. Two spheres of radii 4 cm and 8 cm have the same amount of charge. Determine the ratio of their surface densities of charge.
Answer: 4:1

Question 7. The diameter of a sphere is 2 cm. The sphere is hollow and conducting and is given a charge of 6.16 units. Determine the surface density of charge of the sphere on its outer and inner surfaces in the CGS unit.
Answer: 0.49 CGS unit, 0

Question 8. 64 equally charged water droplets, each of radius 4 mm, are combined to form a large water drop. Determine the ratio of the surface densities of charges in the two cases.
Answer: 4:1

Question 9. The ratio of the radii of two spheres is 5: 2 and that of their charges is 5:3. Determine the ratio of the surface densities of charge of the two spheres.
Answer: 4:15

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Assertion-reason type

Direction: These questions have statement I and statement II. Of the four choices given below, choose the one that best describes the two statements.

1. Statement 1 Is true, statement 2 is true; statement 2 is a correct explanation for statement 1
2. Statement 1 is true, and statement 2 is true; statement 2 Is not a correct explanation for statement 1.
3. Statement 2 is true, statement 2 is false.
4. Statement 1 is false, and statement 2 is true

Question 1.

Statement 1: If there exists attraction between two bodies, both of them may not be charged.

Statement 2: A charged body can attract a neutral body.

Answer: 1. Statement 1 Is true, statement 2 is true; statement 2 is a correct explanation for statement 1

Question 2.

Statement 1: The Mass of a body decreases slightly when it is negatively charged.

Statement 2: Charging is due to the transfer of electrons

Answer:  4. Statement 1 is false, statement 2 Is true

Question 3.

Statement 1: Total charge on a body is the algebraic sum of charges located at different points of the body.

Statement 2: Electric charge is additive in nature.

Answer: 1. Statement 1 Is true, statement 2 is true; statement 2 is a correct explanation for statement 1

Question 4.

Statement 1: The tires of an aircraft are slightly conducting.

Statement 2: If a conductor is grounded, the extra charge induced on the conductor will flow to the ground.

Answer: 1. Statement 1 Is true, statement 2 is true; statement 2 is a correct explanation for statement 1

Question 5.

Statement 1: The top of a lightning conductor of a high building has sharp pointed ends.

Statement 2: The surface density of charge at sharp points is very high, resulting in the setting up of an electric wind.

Answer: 1. Statement 1 Is true, statement 2 is true; statement 2 is a correct explanation for statement 1

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Multiple Choice Question And Answers

In this type of question, more than one option is correct.

Question 1. Two identical metallic spheres are given charges +q and -q respectively. Now

1. Both spheres have equal masses
2. The positively charged sphere has a mass smaller than that of the negatively charged sphere
3. The negatively charged sphere has a mass smaller than that of the positively charged sphere
4. The change in the masses depends on the magnitude of the charge transfer

Answer:

2. The positively charged sphere has a mass smaller than that of the negatively charged sphere

4. The change in the masses depends on the magnitude of charge transfer

Question 2. A spherical conductor A lies inside a hollow spherical conductor B. Charge Q₁ and Q₂ are given to A and B respectively.

1. Charge Q₁ will appear on the outer surface of A
2. Charge -Q₁ will appear on the inner surface of B
3. Charge Q₂ will appear on the outer surface of B
4. Charge Q₁ + Q₂ will appear on the outer surface of B

Answer:

1. Charge Q₁ will appear on the outer surface of A

2. Charge -Q₁ will appear on the inner surface of B

4. Charge Q₁ + Q₂ will appear on the outer surface of B

Question 3. The minimum quantity of charge available in nature is

1. 1C
2. 4.8 x 10^-13 C
3. 1.6 X 10^-1C
4. 4.8 X 10^-10 esu

Answer:

3. 1.6 X 10^-1C

4. 4.8 X 10^-10 esu

Question 4. A, B, and C are three concentric metallic shells. Shell A is the innermost and shell C is the outermost. A is given some charge.

1. The inner surfaces of B and C will have the same charge
2. The inner surfaces of B and C will have the same surface density of charge
3. The outer surfaces of A, B, and C will have the same charge
4. The outer surfaces of A, B, and C will have the same surface density of charge

Answer:

1. The inner surfaces of B and C will have the same charge

3. The outer surfaces of A, B, and C will have the same charge

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Match The Columns

Answer: 1-B, 2-A, 3 D, 4-C

Answer: 1-D, 2-A, 3-B, 4-C

Answer: 1-C, 2-B, 3-E, 4-A

Comprehension type:

Read the following passage carefully and answer the questions at the end of it.

Question 1. A glass rod when rubbed- with silk acquires ‘a. change of +3.2 x 10^-7C.

1. The amount of charge on the silk is

1. 0
2. -3.2 x 10^-7C
3. +1.6 x 10^-7C
4. Not possible to calculate

Answer: 2. +1.6 x 10^-7C

2. Transfer of mass from glass rod to silk is

1. 9 x 10^-19 kg
2. 0
3. 18 x 10^-19 kg
4. None of the above

Answer: 3. 18 x 10^-19 kg

Question 2. A hollow spherical conductor of radius 3 cm is charged with a charge of 36πC.

1. The surface density of charge on the inner surface of the following conductor is

1. 1 C .cm^-2
2. 0
3. 104 C.cm^-2
4. ∞

Answer: 2. 0

2. The surface density of charge on ‘the outer surface of the hollow conductor is

1. 0
2. 1 C.m^-2
3. 104C.m^-2
4. ∞

Answer: 3. 104C. m^-2

3. If the hollow sphere is a solid one, the surface density of charge on its outer surface is

1. 0
2. 1C m^-2
3. ∞
4. 104 C.m^-2

Answer: 4. 104 C.m^-2

Integer answer type:

In this type, the answer to each of the questions is a single-digit integer ranging from 0 to 9:

Question 1. An insulated spherical conductor of radius lm is charged with a positive charge of 8πC. What is the surface density of charge on, the surface of the conductor in C.m^-2?
Answer: 2

Question 2. The surface area of a body is 10 cm? and its surface density of charge is 0.4 unit/cm². What is the total charge on it?
Answer: 4

Question 3. A body has a -0.8 x 10^-18C, charge. What is the number of excess electrons in the body?
Answer: 5

Question 4. A cube of the side has a 72 πC charge. What is the average surface density of charge of the cube in μC.cm^-2?
Answer: 3

Unit 1 Electrostatics Chapter 1 Elementary Phenomena Of Electrostatics Examination Archive With Solutions

Question 1. The number of electrons in 2 C of charge is

1. 12.5 X 10^-18
2. 12.5 X 10(-19)
3. 12.5 X 10¹⁸
4. 12.5 X 10¹⁹

Answer: 3.

Charge of one electron

= 1.6 X 10^-19 C

∴Number of electrons in’ 2 C charge

⇒ \(\frac{2}{1.6 \times 10^{-19}}\)

= 12.5 X 10¹⁸

The option 3 is correct.