Properties of Charge : Additivity, Quantization and Conservation

Properties of Charge 

       Mastering the properties of charge—Additivity, Quantization, and Conservation—is crucial for Class 12 Physics students in CBSE and RBSE. These concepts are vital for board exams and competitive exams like JEE and NEET. Explore these key electrostatics principles with us, based on the NCERT textbook.

Properties of Charge

Additivity:

• The total charge of a system is the algebraic sum of the charges of its constituents.
• Charges of the same sign (both positive or both negative) repel each other, while charges of opposite signs (positive and negative) attract each other.
• This principle allows for the understanding of how charged objects interact with each other.

Quantization:

• Electric charge is quantized, meaning it exists in discrete packets or multiples of a fundamental unit.
• The smallest unit of charge is the charge of an electron, denoted as $e$, which has a magnitude of approximately`1.6×10^{19}` coulombs (C).
• This means that any charge in nature is always some integer multiple of this fundamental charge $e$.
• For example, an object may possess a net charge of $+3e$ or $-2e$, but not a fractional charge like $0.5e$ or $1.3e$.

Conservation:

• Electric charge is a conserved quantity, which means the total electric charge within a closed system remains constant over time.
• In other words, electric charge cannot be created or destroyed; it can only be transferred from one object to another.
• This principle is analogous to the conservation of mass or energy in other physical systems.
• For example, during charging by friction, electrons are transferred from one object to another, but the total charge of the system remains the same.

PROPERTICE OF ELECTRIC cHARGE mcqs

1. What is the smallest unit of electric charge? 

    a) $1.6\times 10^{-9}$ C 

    b) $1.6\times 10^{-12}$ C 

    c) $1.6\times 10^{-19}$ C 

    d) $1.6\times 10^{-23}$ C

2.    Which property of electric charge states that the total charge within a closed system remains constant? 

    a) Quantization 

    b) Conservation 

    c) Additivity 

    d) Induction

3.What does Coulomb's law describe? 

    a) The quantization of electric charge 

    b) The conservation of electric charge 

    c) The behavior of charged particles in electromagnetic fields 

    d) The force between two charged objects

4.Electric charge exists in how many types? 

    a) One 

    b) Two 

    c) Three 

    d) Four

5.    What is the charge of an electron? 

    a) $+1.6 \times 10^{-19}$ C 

    b) $-1.6 \times 10^{-19}$ C 

    c) $+1.6 \times 10^{-9}$   C 

    d) $-1.6 \times 10^{-9}$   C

6.    Which property of electric charge refers to the principle that charges of the same sign repel each other while charges of opposite signs attract? 

    a) Quantization 

    b) Conservation 

    c) Additivity 

    d) Induction

7.    If two objects carry charges of $+2e$ and $-3e$ respectively, what is the total charge of the system? 

    a) $-e$

    b) $+e$

    c) $-5e$

    d) $+5e$

8.    What is the SI unit of electric charge? 

    a) Ampere (A) 

    b) Joule (J) 

    c) Coulomb (C) 

    d) Volt (V)

9.    Electric charge is conserved analogous to which other physical quantity? 

    a) Mass 

    b) Velocity 

    c) Temperature 

    d) Length

Answers:

        1.    c) $1.6\times 10^{-19}$ C
        2.    b) Conservation
        3.    d) The force between two charged objects
        4.    b) Two
        5.    b) $-1.6\times 10^{-19}$ C
        6.    c) Additivity
        7.    a) $-e$

        8.    c) Coulomb (C)

        9.    a) Mass

SHORT ANSWER TYPE QUESTIONS

1. What are the two types of electric charges?

2. State the law of conservation of charge.

3. Define quantization of charge. How is it mathematically expressed?

4. What is the principle of superposition of electric charges?

5. Explain the concept of charge invariance.

6. How does the force between two charges change if the distance between them is doubled?

7. Describe the difference between conductors and insulators with respect to the movement of charges.

8. What is Coulomb’s law? State its mathematical form.

9. Explain the difference between a point charge and a test charge.

10. What is meant by charging by induction? How is it different from charging by conduction?

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