## 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**

- Positively charged
- Earth-connected
- Negatively charged
- 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**

- Positively charged
- Negatively charged
- Uncharged
- Made by metal

**Answer:** 3. Uncharged

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

- Conversion of raindrops into elections
- The electric field of the earth
- Creation of ions by the sun
- 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**

- 1.6 x 10
^{-13}C - 1.6 X 10
^{-25}C - 1.6 x 10
^{-19}C - None of the above

**Answer:** 3. 1.6 x 10^{-19}C

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

- Protons are added to the glass rod
- Protons are removed from the glass rod
- Electrons are added to the glass rod
- 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**

- The two spheres will have equal mass
- The sphere charged negatively will have a greater mass
- The sphere charged positively will have a greater mass
- 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**

- Does not change
- Increases a little
- Decreases a little
- 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?**

- 3.2 x 10
^{-10}C - 4.8 x 10
^{-10}C - 5.6 x 10
^{-19}C - 1.6 x 10
^{-19}C

**Answer:** 3. 5.6 x 10^{-19} C

**Question 9. Electrostatic induction can be brought about**

- In conductors only
- In insulators only
- In bad conductors only
- 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**

- Attract each other with a smaller force
- Attract each other with a greater force
- Repel each other with a smaller force
- 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**

- In all cases
- In the case of solid and hollow conductors
- In the case of only spherical conductors
- 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**

- More charge
- Less charge
- An equal amount of charge
- None of the above

**Answer:** 3. Equal amount of charge

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

- C
- C m
^{-1} - C.m
^{-2} - 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**

- 0
- 1
- 12.56
- 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 10^{18}

**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^{-12}C

**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 ^{-19}C**

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 10^{14}

**Question 2. A conductor is clinked with 14.4 x 10 ^{19}C. 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.

**Statement 1 Is true, statement 2 is true; statement 2 is a correct explanation for statement 1****Statement 1 is true, and statement 2 is true; statement 2 Is not a correct explanation for statement 1.****Statement 2 is true, statement 2 is false.****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 conduc****ting.**

**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**

- Both spheres have equal masses
- The positively charged sphere has a mass smaller than that of the negatively charged sphere
- The negatively charged sphere has a mass smaller than that of the positively charged sphere
- 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 Q _{1} and Q_{2} are given to A and B respectively.**

- Charge Q
_{1}will appear on the outer surface of A - Charge -Q
_{1}will appear on the inner surface of B - Charge Q
_{2}will appear on the outer surface of B - Charge Q
_{1}+ Q_{2}will appear on the outer surface of B

**Answer:**

1. Charge Q_{1} will appear on the outer surface of A

2. Charge -Q_{1} will appear on the inner surface of B

4. Charge Q_{1} + Q_{2} will appear on the outer surface of B

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

- 1C
- 4.8 x 10
^{-13}C - 1.6 X 10
^{-1}C - 4.8 X 10
^{-10}esu

**Answer:**

3. 1.6 X 10^{-1}C

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.**

- The inner surfaces of B and C will have the same charge
- The inner surfaces of B and C will have the same surface density of charge
- The outer surfaces of A, B, and C will have the same charge
- 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 ^{-7}C.**

**1. The amount of charge on the silk is**

- 0
- -3.2 x 10
^{-7}C - +1.6 x 10
^{-7}C - Not possible to calculate

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

**2. Transfer of mass from glass rod to silk is**

- 9 x 10
^{-19}kg - 0
- 18 x 10
^{-19}kg - 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 C .cm
^{-2} - 0
- 104 C.cm
^{-2} - ∞

**Answer:** 2. 0

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

- 0
- 1 C.m
^{-2} - 104C.m
^{-2} - ∞

**Answer:** 3. 104C. m^{-2}

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

- 0
- 1C m
^{-2} - ∞
- 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 ^{-18}C, 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**

- 12.5 X 10
^{-18} - 12.5 X 10(-19)
- 12.5 X 10
^{18} - 12.5 X 10
^{19}

**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 10^{18}

The option 3 is correct.