We often observe a spark or hear a crackling sound, when we take off our woollen clothes. Apart from this, sometimes we experience a sensation of a light shock while opening the door of the car or after sliding from the seat. It happens due to the discharge of Electric charge through our body,
So, In this article, we will cover the concept of Electric Charge. This concept falls under the broader category of Electrostatics which is a crucial chapter in Class 12 physics.
In the class 12 Physics electric charge is the important topic and numerical questions and its types are often asked in the exams. Let's discuss the Electric charges and fields in detail.
Electric charge is a physical attribute of particles that gives these particles a force within an electric field. It is the source of the electromagnetic force, one of the four basic force in the nature, which explain interaction between charges particles.
Students are confused whether Charge is a scalar and vector quantity. Answer to this question is that Charge is a scalar quantity.
The SI unit of electric charge is the coulomb, represented by the symbol "C".
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There are two types of electric charges-positive and negative.
Like charges (Positive-Positive or Negative-Negative) repel each other (glass rods rubbed with wool or silk repel each other) and unlike charges ( Positive-Negative) attract each other (glass rod and wool attract each other).
Additivity: If a system contains n charge $q_1, q_2, q_3 \ldots \ldots q_n$, then the total charge of the system is $q_1+q_2+\ldots \ldots q_n$.
Conservation of Charge: The charge can be neither created nor destroyed. When we rub a glass rod with silk there is a transfer of charge and not creation. The total charge of an isolated system is always conserved.
Unit of Charge: The unit of electric charge is the coulomb (C).
The charge of a single electron is approximately $-1.6 \times 10^{-19}$ coulombs.
Similarly, a proton has a charge of $+1.6 \times 10^{-19}$ coulombs.
Quantization: The charge on a body will be some integral multiple of e, where e is the charge of the electron.
$e=1.6 \times 10^{-19} \mathrm{C}$
Related Topics
Force between two points charges is explained by the Coloumb's law.
Coloumb's law states that: "The magnitude of the electrostatic force (F) between two point charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them."
Mathematcally it is represented by:
$$
F=k \frac{\left|q_1 \cdot q_2\right|}{r^2}
$$
where:
Example 1: Charge on $\alpha$-particle is:
1) $4.8 \times 10^{-19} \mathrm{C}$
2) $1.6 \times 10^{-19} \mathrm{C}$
3) $3.2 \times 10^{-19} \mathrm{C}$
4) $6.4 \times 10^{-19} \mathrm{C}$
Solution:
Electric charge
It is the property associated with matter due to which it produces and experiences electrical and magnetic effects.
Alpha particles have a charge of +2 ,
Hence, the charge on an alpha particle is twice the electron charge
$$
\begin{aligned}
& =2 \times 1.6 \times 10^{-19} \mathrm{C} \\
& \mathrm{q}=3.2 \times 10^{-19}
\end{aligned}
$$
Hence, the answer is the option (3).
Example 2: Which of the following charges is not possible?
1) $1.6 \times 10^{-18} \mathrm{C}$
2) $1.6 \times 10^{-19} \mathrm{C}$
3) $1.6 \times 10^{-20} \mathrm{C}$
4) None of these
Solution:
$1.6 \times 10^{-20} \mathrm{C}$, because this is $\frac{1}{10}$ of electronic charge and hence not an integral multiple.
Hence, the answer is the option (3).
Example 3: When 1019 electrons are removed from a neutral metal plate, the electric charge on it is
1) $ -1.6 C$
2) $+1.6 C$
3) $10^{+19} \mathrm{C}$
4) $10^{-19} \mathrm{C}$
Solution:
Electric charge -The loss of electrons gives a positive charge.
By using
$Q=n e \Rightarrow Q=10^{19} \times 1.6 \times 10^{-19}=+1.6 C$
Hence, the answer is the option (2).
Example 4: When a body is earth-connected, electrons from the earth flow into the body. This means the body is
1) Unchanged
2) Charged positively
3) Charged negatively
4) An insulator
Solution:
When a positively charged body is connected to the earth, electrons flow from the earth to the body and the body becomes neutral.
Example 5: A conductor has $14.4 \times 10^{-19}$ coulombs positive charge. The conductor has (Charge on electron $=1.6 \times 10^{-19}$ coulombs )
1) 9 electrons in excess
2) 27 electrons in short
3) 27 electrons in excess
4) 9 electrons in short
Solution:
Electric charge
The loss of electrons gives a Positive charge
A positive charge shows the deficiency of electrons.
Number of electrons $=\frac{14.4 \times 10^{-19}}{1.6 \times 10^{-19}}=9$
Hence, the answer is the option (4).
Electric charge is a conserved feature of certain subatomic particles that determines their electromagnetic interaction. Electric charge is divided into two types: positive and negative, which are carried by protons and electrons, respectively. When electrons are transported to or withdrawn from an object, an electrical charge is generated. When electrons are introduced to an object, it becomes negatively charged since electrons have a negative charge. When an object's electrons are withdrawn, it will become oppositely charged.
Formula for charge, Q=It
Properties of Electric charge:
A scalar quantity is charge. Charge is transferable; it can move from one body to another. Charge is constantly linked to mass, and similar electric charges repel one another. Electric charges that are opposite one other tend to attract each other.
Charge is a physical attribute that causes matter in an electromagnetic field to experience a force. In the presence of other matter with charge, charge is the fundamental feature of matter that exhibits electrostatic attraction or repulsion. When a charge is at rest, it only creates an electric field. Both an electric and a magnetic field are created when a charge moves.
The presence of an electric charge causes a modification in space known as the electric field. The electric force between a source charge and a test charge is mediated by the electric field. The field is a vector, thus it points away from positive charges and toward negative charges by definition.
The coulomb (C), named after French physicist Charles-Augustin de Coulomb, is the SI-derived unit of electric charge.
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