# Electrostatics

## Overview

Welcome to the world of electrostatics, a fascinating branch of physics that delves into the study of stationary electric charges and their interactions. In this course material, we will embark on a journey to unravel the mysteries behind the existence of positive and negative charges in matter, the different methods of charging a body, the intricacies of Coulomb's inverse square law, and much more.

At the core of electrostatics lies the concept of charges, where we will learn to identify the fundamental properties of positive and negative charges. Understanding how objects become charged through friction, contact, and induction will be essential as we explore the behavior of charged bodies in different scenarios.

One of the key tools in electrostatics is the electroscope, which allows us to detect the presence of electric charges and understand their nature. We will examine the construction and working principles of the electroscope, learning how it can be used to determine the presence and magnitude of charges.

Coulomb's inverse square law governs the interaction between charges, dictating the force between them based on their magnitudes and separation distances. By applying this law, we will delve into solving problems related to electrostatics and analyzing the behavior of charged particles in various configurations.

As we progress through the course material, we will deduce expressions for electric field intensity and potential difference, crucial concepts that help us understand the influence of charges on their surroundings. Exploring the electric field flux patterns generated by isolated and interacting charges will provide insights into the spatial distribution of electric forces.

Moreover, we will analyze how charges distribute themselves on conductors and investigate the role of lightning conductors in protecting structures from electrical discharges. By studying the principles of electrostatics, we will uncover the mechanisms behind phenomena such as electric discharge and lightning, enriching our understanding of the natural forces at play.

## Objectives

1. Identify Electric Field Flux Patterns of Isolated and Interacting Charges
2. Apply Coulomb’s Square Law of Electrostatics to Solve Problems
3. Identify Charges
4. Analyse the Distribution of Charges on a Conductor and How it is Used in Lightning Conductors
5. Deduce Expressions for Electric Field Intensity and Potential Difference
6. Examine Uses of an Electroscope

## Lesson Note

Electrostatics is the branch of physics that deals with the study of electric charges at rest. It encompasses various concepts such as electric fields, potentials, charge distributions, and their interactions. Understanding electrostatics is fundamental, as it provides insights into various phenomena like lightning and the functioning of electronic devices.

## Lesson Evaluation

Congratulations on completing the lesson on Electrostatics. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

1. What is the fundamental property that gives rise to electric charge? A. Mass B. Volume C. Density D. Protons and Electrons Answer: D. Protons and Electrons
2. How can a body be charged by induction? A. By rubbing against another body B. By direct contact with a charged body C. By bringing a charged object close without contact D. By immersing in an electric field Answer: C. By bringing a charged object close without contact
3. What instrument is used to detect the presence of electric charge? A. Ammeter B. Voltmeter C. Electroscope D. Barometer Answer: C. Electroscope
4. What law describes the force between two charged objects? A. Newton's First Law B. Ohm's Law C. Coulomb's Law D. Hooke's Law Answer: C. Coulomb's Law
5. What is the SI unit of electric charge? A. Ampere B. Joule C. Ohm D. Coulomb Answer: D. Coulomb
6. What is the direction of the electric field intensity at a point due to a positive charge? A. Away from the charge B. Towards the charge C. Parallel to the charge D. Perpendicular to the charge Answer: A. Away from the charge
7. How does lightning occur during a storm? A. Due to magnetic field interactions B. Due to gravitational force C. Due to the flow of electric charges between clouds and the ground D. Due to radioactive decay Answer: C. Due to the flow of electric charges between clouds and the ground
8. What is the relationship between electric potential and electric field intensity? A. Directly proportional B. Inversely proportional C. No relationship D. Exponential relationship Answer: B. Inversely proportional
9. What is the purpose of lightning conductors on buildings? A. To attract lightning B. To repel lightning C. To conduct lightning safely to the ground D. To store lightning energy Answer: C. To conduct lightning safely to the ground

## Past Questions

Wondering what past questions for this topic looks like? Here are a number of questions about Electrostatics from previous years

Question 1

(a)(i) State Coulomb's law of electrostatics.

(ii) The electron and proton of a hydrogen atom are separated by a mean distance of 5.2 x 10?11 ${}^{?11}$m.

Calculate the magnitude of the electrostatic force between the particles.

[e = 1.6 x 10?19 ${}^{?19}$ C, (4?  E0 )?1 ${}^{?1}$ = 9.0 x 109 ${}^{9}$ mF1 ${}^{1}$]

(b) The diagram below shows a potential divider circuit.

i. Show that Vout  = Vin  (R1R1+R2)

ii. If VinVout  = 2.5 and R2 ${}_{2}$ = 30? $\mathrm{?}$, calculate R1 ${}_{1}$

iii. Define the volt.

(c) Explain why wood is not suitable for use as the core of transformers.

(d) State one application for the cathode ray tube.

Question 1

Which of the following is NOT an example of elementary modern physics?

Practice a number of Electrostatics past questions