Midterm Exam Overview

This study guide summarizes the key topics and exam preparation details for the PHY1020U midterm, covering lectures 1–14 and textbook chapters 22–28. The focus is on electric charges, electric fields, Gauss's law, electric potential, capacitance, and basic circuit analysis.

Exam Logistics and Preparation

• Date & Time: Section 1: Monday, March 9; Section 54: Tuesday, March 10, 3:40–4:50 PM.

• Location: BIT 2080 (same as lecture room).

• Format: Combination of long-answer and multiple-choice questions.

• Coverage: Lectures 1–14; Chapters 22–28.

• Resources: In-class notes, textbook, tutorials, homework, and online modules.

Electric Charges, Forces, and Fields (Chapter 22–23)

Electric Charge

• Definition: Electric charge is a fundamental property of matter responsible for electric forces and interactions.

• Types: Positive and negative charges; like charges repel, unlike charges attract.

• Unit: Coulomb (C).

• Conservation: Total electric charge is conserved in isolated systems.

Coulomb's Law

• Force between two point charges:

• Where , and are charges, and is the distance between them.

Electric Field

• Definition: The electric field E at a point is the force per unit charge experienced by a small positive test charge placed at that point.

• Formula for a point charge:

• Superposition Principle: The net electric field due to multiple charges is the vector sum of the fields produced by each charge.

• Continuous Charge Distributions: For a continuous distribution, integrate over the charge:

• Inside Capacitors: The electric field between parallel plates (neglecting edge effects):

• Where is the surface charge density.

Electric Flux and Gauss's Law (Chapter 24)

Electric Flux

• Definition: Electric flux through a surface is the product of the electric field and the area perpendicular to the field.

• Formula:

Gauss's Law

• Statement: The net electric flux through any closed surface is proportional to the total charge enclosed within that surface.

• Mathematical Form:

• Applications: Useful for finding electric fields of highly symmetric charge distributions (spheres, cylinders, planes).

Electric Potential and Potential Energy (Chapters 25–26)

Electric Potential (V)

• Definition: The electric potential at a point is the electric potential energy per unit charge at that point.

• Formula for a point charge:

• Relation to Electric Field:

• Potential Difference: Work done per unit charge to move between two points.

Electric Potential Energy (U)

• Definition: The energy a charge has due to its position in an electric field.

• Relation to Potential:

• Multiple Charges/Continuous Distributions: Use superposition and integration as needed.

Capacitors and Capacitance

• Capacitance (C): The ability of a system to store charge per unit potential difference.

• Formula for parallel-plate capacitor:

• Where is plate area, is separation.

Circuits I: Batteries, Capacitors, and Capacitance (Chapter 26)

Capacitors in Series and Parallel

• Series:

• Parallel:

Electric Current and Resistance (Chapter 27)

Electric Current (I)

• Definition: The rate of flow of electric charge.

• Formula:

Resistance (R)

• Definition: Opposition to the flow of electric current.

• Ohm's Law:

• Unit: Ohm ().

Circuits II: Resistors and Kirchhoff's Laws (Chapter 28)

Resistors in Series and Parallel

• Series:

• Parallel:

Kirchhoff's Laws

• Junction Law (Current Law): The sum of currents entering a junction equals the sum leaving it.

• Loop Law (Voltage Law): The sum of potential differences around any closed loop is zero.

Exam Strategies and Requirements

• Arrive early; bring valid photo ID (student or government-issued, in English).

• No phones, smart devices, or unauthorized materials allowed.

• Only writing instruments and scientific calculators permitted.

• Show all steps, equations, and diagrams in solutions; marks are deducted for missing steps or diagrams.

• Use only equations from the provided equation sheet.

• Express vectors with magnitude and angle (counterclockwise from positive x-axis) unless otherwise specified.

• Familiarize yourself with the equation sheet before the exam.

Summary Table: Key Formulas

Additional info:

• For all vector quantities, always specify both magnitude and direction.

• When using Gauss's law, choose a Gaussian surface that matches the symmetry of the charge distribution.

• Practice problems involving superposition, field calculations, and circuit analysis for mastery.