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Physics · 100 Level
This is the complete lecture note for PHY 102 GENERAL PHYSICS 2, prepared for Physics students at 100 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course Code: PHY 102 Course Title: General Physics II (Electricity & Magnetism) Course Unit: 2 Units Series 1: Electrostatics and Electric Fields Series 2: Capacitance, Conductors, and DC Circuits Series 3: Magnetism and Magnetic Properties Series 4: Electromagnetic Induction and Transformers Series 5: Maxwell’s Equations, Oscillations, and AC Circuits Series 1: Electrostatics and Electric Fields Series outline • Part 1: Electric Charge and Coulomb’s Law • 1.1: Properties of Electric Charge • 1.2: Methods of Charging • 1.3: Coulomb’s Law and Superposition Principle • Part 2: Electric Field and Electric Potential • 2.1: Definition and Representation of Electric Field • 2.2: Electric Potential and Potential Energy • 2.3: Relationship between Electric Field and Potential • Part 3: Gauss’s Law and Applications • 3.1: Statement and Physical Meaning of Gauss’s Law • 3.2: Applications to Symmetric Charge Distributions • 3.3: Electric Dipoles and Field Behaviour • Part 4: Energy in Electric Fields • 4.1: Energy Stored in a System of Charges • 4.2: Energy Density in Electric Fields • 4.3: Practical Implications in Physics and Engineering Introduction Electricity is one of the most fundamental forces shaping our modern world, from the operation of household appliances to the transmission of information across global networks. At the heart of electricity lies the concept of electrostatics, which deals with stationary charges and the forces they exert. Understanding electrostatics provides the foundation for grasping more
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS advanced topics in electromagnetism, making this Series an essential starting point in our exploration of General Physics II. The aim of this Series is to equip you with the ability to define, explain, and analyse the behaviour of electric charges, electric fields, and potentials, as well as to apply Gauss’s law and evaluate the energy stored in electric fields. We shall commence this Series by examining the nature of electric charge and Coulomb’s law, including the principle of superposition. Next, we will move on to the concepts of electric field and electric potential, exploring how they are defined and related. Following that, we will consider Gauss’s law and its applications to symmetric charge distributions, including the behaviour of electric dipoles. Finally, we will conclude by analysing how energy is stored in electric fields and its practical implications in physics and engineering. Series Learning Outcomes Upon completing this Series, you should be able to: • 1.1 define the properties of electric charge and distinguish between conductors and insulators, • 1.2 describe methods of charging and demonstrate simple charging processes, • 1.3 explain Coulomb’s law and apply it to calculate forces between point charges, • 1.4 apply the principle of superposition to determine net electrostatic forces in multi-charge systems, • 1.5 describe the concept of electric field and illustrate its representation using field lines, • 1.6 calculate electric field strength for simple charge distributions, • 1.7 explain electric potential and potential energy, and analyse their relationship with electric field, • 1.8 state Gauss’s law and evaluate its physical meaning in relation to flux, • 1.9 apply Gauss’s law to symmetric charge distributions such as spheres, cylinders, and planes, • 1.10 analyse the behaviour of electric dipoles in uniform and non-uniform electric fields, • 1.11 evaluate the energy stored in systems of charges and in continuous electric fields, and • 1.12 discuss practical implications of energy in electric fields for physics and engineering applications. 1.1 Electric Charge And Coulomb’s Law 1.1.1 Properties of electric charge An electric charge is a fundamental property of matter that causes particles to experience a force when placed in an electric field. Charges can be positive or negative, with like charges repelling each other and unlike charges attracting. The unit of charge is the coulomb (C), defined as the quantity of electricity transported in one second by a current of one ampere. Charges are quantised, meaning they exist in discrete amounts, typically as multiples of the elementary charge carried by electrons and protons. Another important property is that charge is conserved, which means the total charge in an isolated system remains constant. Fill in the blank: The unit of electric charge is the ______.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1 Attraction and repulsion of charges 1.1.2 Methods of charging There are three main methods of charging objects: friction, conduction, and induction. • Friction occurs when two different materials are rubbed together, causing electrons to transfer from one material to the other. • Conduction involves direct contact between a charged object and a neutral one, allowing electrons to move freely. • Induction occurs when a charged object is brought near a neutral conductor, causing a redistribution of charges without direct contact. Fill in the blank: When a charged object is brought near a neutral conductor without touching it, the process is called ______.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Plate 1.1 Charging by friction 1.1.3 Coulomb’s law and superposition principle Coulomb’s law states that the magnitude of the electrostatic force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. Mathematically, [ F = k \frac{q_1 q_2}{r^2} ] where (F) is the force, (q_1) and (q_2) are the charges, (r) is the distance between them, and (k) is Coulomb’s constant. The superposition principle states that when multiple charges are present, the net force on a given charge is the vector sum of the individual forces exerted by each of the other charges. This principle is essential for analysing systems with more than two charges. Fill in the blank: According to Coulomb’s law, the force between two charges is inversely proportional to the ______ of the distance between them.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.2 Coulomb’s law representation Box 1.1 Key points of Coulomb’s law Pilot questions 1.1 1. Which property of electric charge ensures that the total charge in an isolated system remains constant? 2. Name one everyday example of charging by friction. 3. State Coulomb’s law in words.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 4. What does the superposition principle allow us to calculate in multi-charge systems? 5. In Coulomb’s law, what happens to the force if the distance between charges is doubled? 1.2 Electric Field And Electric Potential 1.2.1 Definition and representation of electric field An electric field is a region around a charged particle where other charges experience a force. It is defined as the force per unit charge acting on a small positive test charge placed at a point. Mathematically, [ E = \frac{F}{q} ] where (E) is the electric field, (F) is the force, and (q) is the test charge. Electric fields are represented by field lines, which show the direction of the force on a positive test charge. Field lines radiate outward from positive charges and inward towards negative charges. The density of the lines indicates the strength of the field. Fill in the blank: Electric field lines radiate ______ from positive charges and ______ towards negative charges. Figure 1.3 Electric field representation 1.2.2 Electric potential and potential energy Electric potential is the work done per unit charge in bringing a small positive test charge from infinity to a point in the field. It is measured in volts (V). The electric potential energy of a charge is the energy it possesses due to its position in an electric field. The relationship between potential difference and work is given by: [ V = \frac{W}{q} ] where (V) is the potential difference, (W) is the work done, and (q) is the charge. Fill in the blank: Electric potential is measured in ______.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.4 Equipotential lines around a charge 1.2.3 Relationship between electric field and potential The electric field and electric potential are closely related. The electric field is the negative gradient of the potential, meaning it points in the direction of decreasing potential. This relationship is expressed as: [ E = -\frac{dV}{dx} ] This shows that the electric field is strongest where the potential changes most rapidly. Equipotential lines are always perpendicular to electric field lines. Fill in the blank: Equipotential lines are always ______ to electric field lines.
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