⚡ Chapter 15: Electrostatics – Short Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This chapter covers Coulomb's law, electric field, electric potential, capacitance, charging by induction, gold leaf electroscope, lightning, corona discharge, and applications of electrostatics. Each short question is presented with the exact exam-ready answer as per the official PECTAA 2026 Physics curriculum. Perfect for Punjab Boards (Lahore, Gujranwala, Multan, etc.) and all BISE boards across Pakistan.
📚 Related Resources – Chapter 15: Electrostatics
Electrostatics covers Coulomb's law, electric field, potential, capacitance, charging by induction, electroscope, lightning, corona discharge, and applications. Includes solved examples and numerical problems.
📑 Quick Jump to Questions
📖 Short Questions & Answers (PECTAA 2026)
1. Define electrostatics.
Electrostatics is a branch of physics which deals with the study of charges at rest. It focuses on understanding the interaction between charges and electric field they create.
Electrostatics is a branch of physics which deals with the study of charges at rest. It focuses on understanding the interaction between charges and electric field they create.
2. What is electric charge? Explain with examples.
The attraction or repulsion between objects is due to a property called electric charge.
Explanation: When a plastic comb (or rod) is rubbed through dry hair and is brought near small pieces of paper, it attracts them. Similarly, an amber rod when rubbed with silk attracts small pieces of paper. In each of these cases, the electrostatic force resulting from electric charges is in action.
The attraction or repulsion between objects is due to a property called electric charge.
Explanation: When a plastic comb (or rod) is rubbed through dry hair and is brought near small pieces of paper, it attracts them. Similarly, an amber rod when rubbed with silk attracts small pieces of paper. In each of these cases, the electrostatic force resulting from electric charges is in action.
3. What are the types of electric charges? State their SI unit.
There are two types of electric charges, known as positive and negative.
The SI unit of charge is the coulomb (C).
There are two types of electric charges, known as positive and negative.
The SI unit of charge is the coulomb (C).
4. Explain the electrostatic interactions between charged glass rods and plastic rods.
Two glass rods rubbed with silk acquire positive charges and repel each other. Two plastic rods rubbed with wool or fur acquire negative charges and also repel each other. However, a positively charged glass rod and a negatively charged plastic rod attract each other.
Two glass rods rubbed with silk acquire positive charges and repel each other. Two plastic rods rubbed with wool or fur acquire negative charges and also repel each other. However, a positively charged glass rod and a negatively charged plastic rod attract each other.
5. State the basic law of electrostatics.
The basic law of electrostatics states that like charges repel each other, while opposite charges attract each other.
The basic law of electrostatics states that like charges repel each other, while opposite charges attract each other.
6. What are the properties of charges?
Matter is composed of atoms, which consist of subatomic particles. Protons are positively charged particles located in the nucleus, while electrons are negatively charged particles that orbit around the nucleus. Since everything is composed of atoms, every material carries either a positive charge, a negative charge, or is neutral. Charge is an essential property of materials that causes them to either attract or repel.
Matter is composed of atoms, which consist of subatomic particles. Protons are positively charged particles located in the nucleus, while electrons are negatively charged particles that orbit around the nucleus. Since everything is composed of atoms, every material carries either a positive charge, a negative charge, or is neutral. Charge is an essential property of materials that causes them to either attract or repel.
7. Define electrostatic induction.
In the presence of a charged object, an insulated conductor develops a positive charge at one end and a negative charge at the other end. This process is known as electrostatic induction.
In the presence of a charged object, an insulated conductor develops a positive charge at one end and a negative charge at the other end. This process is known as electrostatic induction.
8. What is charging by induction?
Charging by induction is a method of charging a conductor without directly touching it with a charged object. It involves the redistribution of electric charges within a conductor when exposed to a nearby electric field.
Charging by induction is a method of charging a conductor without directly touching it with a charged object. It involves the redistribution of electric charges within a conductor when exposed to a nearby electric field.
9. What is earthing?
Earthing is the process of connecting a conductor to the Earth using a conducting wire.
Earthing is the process of connecting a conductor to the Earth using a conducting wire.
10. What is a gold leaf electroscope?
The gold leaf electroscope is a sensitive device used to detect electric charges. It consists of a brass rod with a brass disk at the top and two thin gold leaves suspended at the bottom. The rod passes through an insulating material, allowing charges to move freely from the disk to the leaves.
The gold leaf electroscope is a sensitive device used to detect electric charges. It consists of a brass rod with a brass disk at the top and two thin gold leaves suspended at the bottom. The rod passes through an insulating material, allowing charges to move freely from the disk to the leaves.
11. How does a gold leaf electroscope detect electric charge?
To detect the presence of charge on an object, bring the object near the disk of an uncharged electroscope. If the object is neutral, there will be no deflection of the leaves. However, if the object is charged either positively or negatively the leaves of the electroscope will diverge. The extent of the divergence depends on the amount of charge present on the object.
To detect the presence of charge on an object, bring the object near the disk of an uncharged electroscope. If the object is neutral, there will be no deflection of the leaves. However, if the object is charged either positively or negatively the leaves of the electroscope will diverge. The extent of the divergence depends on the amount of charge present on the object.
12. Explain the working of a gold leaf electroscope with a negatively charged object.
If the object is negatively charged, electrostatic induction will cause a positive charge to appear on the disk and a negative charge to accumulate on the leaves. Since both leaves carry the same charge, they will repel each other and move apart.
If the object is negatively charged, electrostatic induction will cause a positive charge to appear on the disk and a negative charge to accumulate on the leaves. Since both leaves carry the same charge, they will repel each other and move apart.
13. How can a gold leaf electroscope distinguish between conductors and insulators?
Bring a charged object near the disk of the electroscope without touching it. If the gold leaves collapse from their previously diverged position, the material is a good conductor, because charge can flow. If the leaves do not collapse, the material is an insulator.
Bring a charged object near the disk of the electroscope without touching it. If the gold leaves collapse from their previously diverged position, the material is a good conductor, because charge can flow. If the leaves do not collapse, the material is an insulator.
14. Rub a balloon on your dry hair and then hold it close to a wall. The balloon sticks to the wall. But why does this happen when the wall is not charged?
The balloon becomes charged by friction. It induces an opposite charge on the neutral wall through electrostatic induction. Since unlike charges attract, the balloon sticks to the wall.
The balloon becomes charged by friction. It induces an opposite charge on the neutral wall through electrostatic induction. Since unlike charges attract, the balloon sticks to the wall.
15. Why do the leaves of an electroscope diverge when a charged object is brought near, even if the object does not touch the electroscope?
The charged object induces opposite charges on the disk and leaves of the electroscope through electrostatic induction. Since both leaves get the same charge, they repel each other and diverge.
The charged object induces opposite charges on the disk and leaves of the electroscope through electrostatic induction. Since both leaves get the same charge, they repel each other and diverge.
16. What are the applications of electrostatics with conductors?
There are many applications of electrostatics with conductors. Charging and discharging are fundamental processes in the operation of various devices, such as photocopiers and electrostatic precipitators, which rely on electrostatic principles.
There are many applications of electrostatics with conductors. Charging and discharging are fundamental processes in the operation of various devices, such as photocopiers and electrostatic precipitators, which rely on electrostatic principles.
17. What is a photocopier?
A photocopier is an electronic machine used to make copies of documents and images. It works on a process called xerography. The xerography is derived from the Greek words "xeros" (dry) and "graphos" (writing), meaning "dry writing."
A photocopier is an electronic machine used to make copies of documents and images. It works on a process called xerography. The xerography is derived from the Greek words "xeros" (dry) and "graphos" (writing), meaning "dry writing."
18. What is an electrostatic precipitator (ESP)?
An electrostatic precipitator (ESP) is a device used to remove particulate matter from industrial exhaust gases.
An electrostatic precipitator (ESP) is a device used to remove particulate matter from industrial exhaust gases.
19. What is corona discharge?
Corona discharge is an electrical phenomenon where a high-voltage ionizes the air around a conductor (e.g., a thin wire), creating a plasma region that releases electrons. These electrons attach to nearby gas molecules, forming negative ions.
Corona discharge is an electrical phenomenon where a high-voltage ionizes the air around a conductor (e.g., a thin wire), creating a plasma region that releases electrons. These electrons attach to nearby gas molecules, forming negative ions.
20. Define Coulomb's law.
Coulomb's law states that; The magnitude of the electrostatic force between two point charges is directly proportional to the product of magnitude of these charges and inversely proportional to the square of the distance between them. Mathematically, it is given by
\[F = k\frac{q_1q_2}{r^2}\]
If the medium between the two charges is air, then the value of \(k\) in SI units will be \(9 \times 10^9 Nm^2 C^{-2}\).
Coulomb's law states that; The magnitude of the electrostatic force between two point charges is directly proportional to the product of magnitude of these charges and inversely proportional to the square of the distance between them. Mathematically, it is given by
\[F = k\frac{q_1q_2}{r^2}\]
If the medium between the two charges is air, then the value of \(k\) in SI units will be \(9 \times 10^9 Nm^2 C^{-2}\).
21. What is a point charge?
A point charge is a charge whose size is negligible compared to the distance separating it from other charges. Coulomb's law is applicable primarily to such point charges.
A point charge is a charge whose size is negligible compared to the distance separating it from other charges. Coulomb's law is applicable primarily to such point charges.
22. Define electric field.
An electric field is the region around a charge where it exerts a force on other charges. Mathematically
\[E = k\frac{q}{r^2}\]
An electric field is the region around a charge where it exerts a force on other charges. Mathematically
\[E = k\frac{q}{r^2}\]
23. Define electric field intensity. Also write its SI unit.
The electrostatic force per test charge (unit positive charge) when it is brought to the electric field of a source charge is called electric field intensity. Mathematically
\[E = \frac{F}{q_0}\]
The SI unit of electric field intensity is newton per coulomb \((NC^{-1})\).
The electrostatic force per test charge (unit positive charge) when it is brought to the electric field of a source charge is called electric field intensity. Mathematically
\[E = \frac{F}{q_0}\]
The SI unit of electric field intensity is newton per coulomb \((NC^{-1})\).
24. Why is electric field intensity a vector quantity?
Electric field intensity is a vector quantity because it has both magnitude and direction. Its direction is the same as the direction of the force on a positive test charge.
Electric field intensity is a vector quantity because it has both magnitude and direction. Its direction is the same as the direction of the force on a positive test charge.
25. What are electric field lines? Also state its properties.
Electric field lines are imaginary lines that represent an electric field and show the direction of the force at a point.
Properties:
(i) Electric field direction is from a positive charge to a negative charge.
(ii) Electric field lines do not cross each other.
(iii) Electric field lines represent the path that a small positive test charge would follow in an electric field.
Electric field lines are imaginary lines that represent an electric field and show the direction of the force at a point.
Properties:
(i) Electric field direction is from a positive charge to a negative charge.
(ii) Electric field lines do not cross each other.
(iii) Electric field lines represent the path that a small positive test charge would follow in an electric field.
26. Describe the electric field around a point charge.
Around a point charge, the electric field is radial, extending outward in all directions. For a positive point charge, the electric field lines radiate outward, indicating that a positive test charge placed nearby would be repelled. In contrast, for a negative point charge, the electric field lines point inward, showing that a positive test charge would be attracted towards it.
Around a point charge, the electric field is radial, extending outward in all directions. For a positive point charge, the electric field lines radiate outward, indicating that a positive test charge placed nearby would be repelled. In contrast, for a negative point charge, the electric field lines point inward, showing that a positive test charge would be attracted towards it.
27. Describe the electric field around a charged conducting sphere.
Around a charged conducting sphere, the electric field lines are radial, radiating outward for a positively charged sphere and inward for a negatively charged sphere. Inside the sphere, the electric field is zero.
Around a charged conducting sphere, the electric field lines are radial, radiating outward for a positively charged sphere and inward for a negatively charged sphere. Inside the sphere, the electric field is zero.
28. Describe the electric field between two oppositely charged parallel conducting plates.
A uniform electric field is created between them. The electric field lines point from the positively charged plate to the negatively charged plate, and they are parallel and equally spaced, showing a uniform electric field. This uniformity means the electric field has the same magnitude and direction at all points between the plates.
A uniform electric field is created between them. The electric field lines point from the positively charged plate to the negatively charged plate, and they are parallel and equally spaced, showing a uniform electric field. This uniformity means the electric field has the same magnitude and direction at all points between the plates.
29. Why are people inside metal cars or airplanes safe during lightning strikes?
People inside metal cars or airplanes are safe during lightning strikes because the electric field inside a charged conducting sphere is always zero.
People inside metal cars or airplanes are safe during lightning strikes because the electric field inside a charged conducting sphere is always zero.
30. Differentiate between electrical conductors and insulators.
| Electrical Conductors | Electrical Insulators |
|---|---|
| Electrical conductors are materials that allow electric charge to flow freely through them. | Electrical insulators are materials that resist or prevent the flow of electric charge. |
| For example, copper, aluminium, silver, graphite and electrolytes. | For example, rubber, plastic, glass, wood and ceramics. |
31. Explain the free electron model of conductors and insulators.
In conductors, the outermost electrons are loosely bound and can move freely, allowing electric current to flow. In insulators, the electrons are tightly bound to their atoms and cannot move freely. This difference explains why conductors allow electricity to flow while insulators block it.
In conductors, the outermost electrons are loosely bound and can move freely, allowing electric current to flow. In insulators, the electrons are tightly bound to their atoms and cannot move freely. This difference explains why conductors allow electricity to flow while insulators block it.
32. What is the accumulation of charges?
The accumulation of charges, often referred to as static electricity, occurs when electrons are transferred from one object to another, leading to an imbalance of positive and negative charges.
The accumulation of charges, often referred to as static electricity, occurs when electrons are transferred from one object to another, leading to an imbalance of positive and negative charges.
33. What are the effects (consequences) of accumulation of charges?
In everyday life, accumulated charges can cause minor shocks when touching metal objects or make clothes cling together. In industrial settings, they can damage electronic components, ignite flammable substances, or disrupt manufacturing processes.
In everyday life, accumulated charges can cause minor shocks when touching metal objects or make clothes cling together. In industrial settings, they can damage electronic components, ignite flammable substances, or disrupt manufacturing processes.
34. How can the harmful effects of charge accumulation be prevented?
Proper grounding, anti-static measures, and humidity control are used to mitigate the risks and prevent the harmful effects of charge accumulation.
Proper grounding, anti-static measures, and humidity control are used to mitigate the risks and prevent the harmful effects of charge accumulation.
35. What is electrical breakdown?
Electrical breakdown occurs when a strong electric field passes through a gas (or insulating material), causing its atoms to ionize. This ionization creates free electrons and ions, which can conduct electricity.
Electrical breakdown occurs when a strong electric field passes through a gas (or insulating material), causing its atoms to ionize. This ionization creates free electrons and ions, which can conduct electricity.
36. What happens during electrical breakdown?
When the electric field is strong enough, it can lead to a sudden, dramatic increase in conductivity, often resulting in a spark or arc.
When the electric field is strong enough, it can lead to a sudden, dramatic increase in conductivity, often resulting in a spark or arc.
37. What is corona discharge?
Corona discharge is a visible form of electrical breakdown that occurs when a high-voltage electric field ionizes the air around a conductor, typically near sharp points or edges where the electric field is strongest.
Corona discharge is a visible form of electrical breakdown that occurs when a high-voltage electric field ionizes the air around a conductor, typically near sharp points or edges where the electric field is strongest.
38. Why does a bluish glow appear around high-voltage power lines?
When the electric field around a high-voltage power line becomes intense, it ionizes nearby air molecules, producing corona discharge, which appears as a faint blue or violet glow.
When the electric field around a high-voltage power line becomes intense, it ionizes nearby air molecules, producing corona discharge, which appears as a faint blue or violet glow.
39. What are Lichtenberg figures?
Lichtenberg figures are branching, tree-like patterns that form on insulating materials (like wood or acrylic) when a high-voltage electrical discharge passes through them. They are visible examples of electrical breakdown.
Lichtenberg figures are branching, tree-like patterns that form on insulating materials (like wood or acrylic) when a high-voltage electrical discharge passes through them. They are visible examples of electrical breakdown.
40. What are visible examples of electrical breakdown?
Both corona discharge and Lichtenberg figures are visible examples of electrical breakdown, demonstrating how strong electric fields can ionize materials and create conductive paths.
Both corona discharge and Lichtenberg figures are visible examples of electrical breakdown, demonstrating how strong electric fields can ionize materials and create conductive paths.
41. What are lightning conductors?
Lightning conductors (lightning rods) are protective devices installed on tall structures to safeguard them from lightning strikes.
Lightning conductors (lightning rods) are protective devices installed on tall structures to safeguard them from lightning strikes.
42. How does a lightning conductor protect a building?
A lightning rod provides a low-resistance path for the electrical discharge to follow, directing the current safely into the ground. This prevents fires, structural damage, and harm to humans.
A lightning rod provides a low-resistance path for the electrical discharge to follow, directing the current safely into the ground. This prevents fires, structural damage, and harm to humans.
43. How is lightning produced?
Lightning is produced through charge separation, electric field buildup, and electrical discharge. It begins with the accumulation of electric charge due to friction between water molecules in clouds. When the electric potential difference becomes large enough, it overcomes the resistance of air, causing a rapid discharge of electricity between the cloud and the ground.
Lightning is produced through charge separation, electric field buildup, and electrical discharge. It begins with the accumulation of electric charge due to friction between water molecules in clouds. When the electric potential difference becomes large enough, it overcomes the resistance of air, causing a rapid discharge of electricity between the cloud and the ground.
44. How is cloud-to-ground lightning produced?
The strong electric field of charged clouds induces an opposite charge on the Earth's surface. When the potential difference becomes sufficiently large, air breaks down and a rapid electrical discharge occurs between the cloud and the ground, producing lightning and thunder.
The strong electric field of charged clouds induces an opposite charge on the Earth's surface. When the potential difference becomes sufficiently large, air breaks down and a rapid electrical discharge occurs between the cloud and the ground, producing lightning and thunder.
📐 Key Formulas – Electrostatics
Coulomb's Law: \( F = k \frac{q_1 q_2}{r^2} \)
Electric Field Intensity: \( E = \frac{F}{q_0} \)
Electric Field (Point Charge): \( E = k \frac{q}{r^2} \)
Electric Potential: \( V = \frac{W}{q} \)
Coulomb's Constant: \( k = 9 \times 10^9 \, \text{Nm}^2\text{C}^{-2} \)
Quantization of Charge: \( q = ne \)
Unit 10Thermal Physics
Unit 11Transfer of Thermal Energy
Unit 12Waves
Unit 13Sound
Unit 14Light
Unit 15✨ Electrostatics
Unit 16Electricity
Unit 17Electromagnetism
Unit 18Electromagnetic Induction & EM Waves
Unit 19Electronics
Unit 20Atomic and Nuclear Physics
Unit 21Space and Environment
📖 Complete syllabus coverage for Class 10 Physics (PECTAA 2026) – Units 10 to 21
💡 Exam Tip:
For board exams, define key terms precisely, mention formulas with units, and relate to real-life examples. These questions follow the PECTAA 2026 pattern and are prepared by Subject Specialist Muhammad Tayyab.
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus