If you are looking for Class 10 Physics Unit 13 Electrostatics Notes, you are in the right place. This chapter helps students understand how electric charges are produced and how they behave. Electrostatics is an important unit because it explains the basic ideas of electricity that are used in daily life and modern devices.
In this unit, you will learn about the production of electric charges, electrostatic induction, and the working of an electroscope. You will also study Coulomb’s Law, which explains the force between two electric charges. Other important topics include electrostatic potential, capacitors and capacitance, different types of capacitors, and the applications of electrostatics.
These notes are prepared according to the latest syllabus and exam pattern. In this post, you will find important MCQs, short questions, and long questions to help you prepare for board exams easily and score high marks.
Important MCQs – Unit 13 Electrostatics
1. A positive electric charge:
(a) attracts other positive charge
(b) repels other positive charge ✅
(c) attracts a neutral charge
(d) repels a neutral charge
2. The Coulomb’s law is valid for the charges which are:
(a) moving and point charges
(b) moving and non-point charges
(c) stationary and point charges ✅
(d) stationary and large size charges
3. What happens when two like charges are brought close to each other?
(a) They attract
(b) They merge
(c) They repel ✅
4. According to Coulomb’s law, the electrostatic force is:
(a) Inversely proportional to the product of the charges
(b) Directly proportional to the square of the distance
(c) Inversely proportional to the square of the distance ✅
(d) Independent of distance
Short Questions – Unit 13 Electrostatics
1. State Coulomb’s Law in words.
Answer:
Coulomb’s Law states that:
-
The force between two charged bodies is directly proportional to the product of their charges.
-
The force is inversely proportional to the square of the distance between them.
Equation:
F = k * (q1 * q2) / r^2
Explanation:
-
q1 and q2 are the magnitudes of the charges.
-
r is the distance between the charges.
-
k is Coulomb’s constant.
-
Increasing charges increases the force, increasing distance decreases the force.
2. What is the relation between volt, joule, and coulomb?
Answer:
1 Volt = 1 Joule / 1 Coulomb
(i.e., one volt is the potential when one joule of work is done to move one coulomb of charge.)
Explanation:
-
-
Voltage (V) measures electric potential difference.
-
1 Joule of work done to move 1 Coulomb of charge produces 1 Volt.
-
3. What is an electroscope?
Answer:
An electroscope is a device used to detect the presence, magnitude, and type of electric charge on a body.
Explanation:
-
It can show whether a charge is positive or negative.
-
Common types include gold-leaf electroscope and pith-ball electroscope.
-
Used in labs to study electrostatics and charge distribution.
4. Define electric field intensity.
Answer:
Electric field intensity is the force experienced by a unit positive charge placed at a point in the electric field.
Explanation:
-
It tells us how strong the electric field is at a given point.
-
Formula (plain text):
E = F / q-
E = electric field intensity
-
F = force on the charge
-
q = magnitude of the test charge
-
Long Questions – Unit 13 Electrostatics
Q1: What is Coulomb’s Law? State it and explain the mathematical form of the law with the help of a diagram.
Definition of Coulomb’s Law:
Coulomb’s Law describes the electrostatic force between two charged particles. It tells us how the force depends on the magnitude of the charges and the distance between them.
Statement of the Law:
-
The force of attraction or repulsion between two point charges is:
-
Directly proportional to the product of the magnitudes of the charges.
-
Inversely proportional to the square of the distance between them.
-
-
The force acts along the straight line joining the two charges.
-
If the charges are of same type (both positive or both negative), the force is repulsive.
-
If the charges are opposite (one positive, one negative), the force is attractive.
Mathematical Form:
Where:
-
F = Electrostatic force between the charges (Newton, N)
-
q1, q2 = Magnitudes of the two charges (Coulomb, C)
-
r = Distance between the charges (Meter, m)
-
k = Coulomb’s constant (k ≈ 9 × 10^9 N·m²/C² in air/vacuum)
Explanation:
-
Direct proportionality: If either charge increases, the force increases.
Example: Doubling q1 doubles the force. -
Inverse square law: If the distance between charges doubles, the force becomes one-fourth.
-
Force direction: Always along the line joining the two charges.
Example:
-
q1 = 2 C, q2 = 3 C, r = 2 m, k = 9 × 10^9 N·m²/C²
-
F = 9 × 10^9 × (2 × 3) / (2²)
-
F = 9 × 10^9 × 6 / 4 = 1.35 × 10^10 N
Conditions for Coulomb’s Law:
-
Charges must be point charges (very small compared to distance).
-
Charges must be stationary (not moving).
-
The medium between charges affects the value of k (air or vacuum is standard).
Diagram:
<repulsion>
Distance between charges = r
-
Arrow shows the direction of force (repulsive if charges are same, attractive if opposite).
Summary:
Coulomb’s Law is fundamental in electrostatics. It helps us:
-
Understand how charges interact.
-
Calculate the magnitude and direction of electrostatic forces.
-
Solve numerical problems related to charges and forces.
Download PDF
The full chapter notes are available in PDF format for easy download and revision.
English Medium View English Medium
Urdu Medium View Urdu Medium PDF