Basic Properties of Electrical Charges Important Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. What is the SI unit of electric charge density?

1. C/m
2. C/m²
3. C²/m
4. C/m²

Ans. The correct answer is d. C/m²

Explanation: Electric charge density is defined as the amount of charge per unit area of a surface.

Charge density = Charge/Area

Therefore, 

Unit of charge density = unit of charge/unit of area = C/m²

Ques. Which of the following is not the property of charge?

1. A charge is self-destructive
2. Charge is additive
3. Charge is conserved
4. Quantization of charge

Ans. The correct answer is a. A charge is self-destructive

Explanation: Electric charge is always conserved in nature which means it can neither be created nor be destroyed. Therefore a charge can never be self-destructive.

Ques. What is the SI unit of electric charge?

1. Ampere
2. Volt
3. Coulomb
4. Second

Ans. The correct answer is c. Coulomb

Explanation: The SI unit of electric charge is Coulomb.

Ques. What is the dimensional formula of electric charge?

1. A²T²
2. AT²
3. A²T
4. AT

Ans. The correct answer is d. AT

Explanation: From the definition of electric current, we get

Charge, Q = It

Where

• Q is the electric charge
• I is the current
• t is time

 [dimensions of Q] = [dimensions of I][dimension of time]

[dimensions of Q] = [AT]

Ques. Is electric charge scalar or vector quantity?

Ans. Electric charge is a scalar quantity because its have only magnitude but no sense of direction.

Ques. Which among the following should be the perfect shape of a conductor that can hold a charge for a long time?

1. Spherical
2. Cubical
3. Conical
4. Sharp-edged

Ans. The correct answer is a. Spherical

Explanation: Since a spherical-shaped conductor does not have sharp edges, therefore, there is less chance of discharge of stored charge. 

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Short Answers Questions [2 Marks Questions]

Ques. What is electric charge?

Ans. Electric charge is a fundamental property of a particle due to which it can apply force on other charged particles or uncharged particles.

Ques. State the law of conservation of charge.

Ans. According to the law of conservation of electric charge, a charge can neither be created nor be destroyed but it can transfer from one body to another body.

In an isolated system, the net charge will always remain constant.

Ques. What are the types of electric charges?

Ans. There are two types of electric charge

• Positive charge: The charge associated with a proton is known as a positive charge.
• Negative charge: The charge associated with an electron is known as negative charge.

Ques. State quantization of electric charge.

Ans. According to the quantization of electric charge, a body can have a charge equal to the integral multiple of the elementary charge. I.e.

Q = ne

Where

• Q is the total charge on a body
• n is an integer i.e. 1, 2, 3, 4, etc. which represents the number of elementary particles i.e. electrons or protons.
• e is the charge of an electron or proton

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Long Answers Questions [3 Marks Questions]

Ques. How many electrons are present in one coulomb of charge?

Ans. Given, the total charge, Q = 1 C

Also, we have the charge of an electron. e = 1.6 x 10^-19 C

Applying the principle of quantization of electric charge

Q = ne

Therefore, the number of electrons n = Q/e

⇒ n = 1/1.6 x 10^-19 = 6.25 x 10¹⁸

Ques. What happens if a charged body is brought near an uncharged body?

Ans. When a charged body is kept near an uncharged body then an equal amount of the opposite charge gets induced on the uncharged body. Since the two bodies now have unlike charges on them, hence they attract each other.

Therefore the conclusion is

• It induces an opposite charge on the uncharged body.
• The two bodies attract each other.

Ques. 6 different types of charges are present in an isolated system, the value of the charges are +3 µC, +9 µC, -4 µC, +5 µC, +6 µC, and -2 µC. What is the total charge present in the system?

Ans. According to the additive property of electric charge, the net charge on a system is the sum of individual charges. I.e

Q_net = q₁ + q₂ + q₃ +........+q_n

Therefore, the total charge in the system is given by

Q_TOTAL = + 3 + 9 - 4 + 5 + 6 - 2 = 17 µC

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the factors that affect the magnitude of the force between two charged objects?

Ans. The factors on which the magnitude of the force between two charges depends are

• The magnitude of charges: The force between the two charges is directly proportional to the product of the magnitude of two charges.
• Distance between the charges: The force between two charges is inversely proportional to the square of the distance between them.
• The relative permittivity of the medium: The force between the two charges is inversely proportional to the relative permittivity of the medium in which two charges are placed.

Ques. What is the magnitude of the electric force between the two charges?

Ans. The magnitude of the force between two charges is given by Coulomb’s law.

According to Coulomb’s law, the magnitude of the force of attraction or repulsion between two charges is directly proportional to the magnitude of the product of two charges and inversely proportional to the square of the distance between them.

Mathematically, 

F ∝ q₁q₂ and F ∝ 1/r²

⇒ F ∝ q₁q₂/r²

⇒ F = k q₁q₂/r²

Where k is the constant of proportionality known as Coulomb’s constant also known as electrostatic constant or Force constant.

Ques. What are the basic properties of electric charge?

Ans. The basic properties of electric charges are

• Like charges repel each other and unlike charges attract each other.
• Electric charges are additive in nature: Total charge on a body is the sum of charges in different regions of the body.
• Electric charges are conserved: Charge can neither be created nor be destroyed but it can transfer from one body to another body.
• Electric charges are quantized in nature: Total charge on a body is integral multiples of the basic charge.
• Electric charges are non-relativistic: The magnitude of charge on a body does not vary whatever may be the speed of the body.

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