Direct Current Circuits - Physics (Undergraduate Foundation)

This course covers the movement of electrical charges through circuits that do not change direction. You will learn the exact definitions of current, voltage, and resistance and how they relate through Ohm’s law. The syllabus explains resistivity in different materials, the electromotive force (EMF) provided by power sources, and the internal resistance of batteries. You will master the use of Kirchhoff’s rules to solve complex networks of resistors and power supplies. Mastering these principles is necessary for anyone building or fixing electrical devices and power systems. You will understand why certain wires heat up more than others and how to choose the right components for a circuit. These skills are used daily by electrical engineers, solar technicians, and hobbyists repairing household electronics or designing battery-powered gadgets. Practical knowledge of DC circuits ensures you can calculate power needs and prevent electrical failures in real-world projects. By the end of this course, you will be able to calculate current, voltage, and resistance in any part of a DC circuit using Ohm’s law. You will know how to determine the resistivity of a wire based on its material and physical dimensions. You will gain the ability to distinguish between terminal voltage and EMF while accounting for internal resistance. Most importantly, you will be able to apply Kirchhoff’s current and voltage laws to find unknown values in circuits with multiple loops and junctions. This course is for undergraduate students in engineering or science who need a solid foundation in electricity. It is also suitable for secondary school leavers preparing for university entrance exams or technical vocational training. Even for those not pursuing a degree, the course provides essential logic for electricians and tech enthusiasts who want to understand the science behind the tools they use. Anyone looking to move from basic guessing to precise electrical calculation will find this material vital.

$ 9.99

Enrolment valid for 12 months

This course is also part of the following learning track. You may join the track to gain comprehensive knowledge across related courses.

PHY 102: General Physics II - Electricity and Magnetism

Electricity and magnetism run every home, factory, and phone all over the world. This track builds the technical foundation to master laws governing electrical energy and signals. You will progress from stationary charges to alternating current and electromagnetic waves. It simplifies the NUC CCMAS syllabus into actionable knowledge for solving practical technical problems. The programme is for first-year university and polytechnic students in engineering or physical sciences. It also serves school leavers preparing for university physics or technical entrance exams. Science teachers and technicians who need a solid refresher on core electrical principles will find the material direct and relevant to their work. You will learn to calculate electrical forces, design functional DC and AC circuits, and predict how magnetic fields drive motors and generators. You will master the use of Gauss's Law, Kirchhoff's rules, and Maxwell's equations to solve engineering challenges. Completing this track ensures success in PHY 102 exams and prepares you for a career in power systems, telecommunications, or renewable energy.

Course Chapters

1. Introduction

This chapter establishes the foundational language of electric circuits, defining the three core quantities you will use throughout the course: current, voltage, and resistance. You will learn how charge flows through conductors and how the macroscopic behaviour of a circuit links back to the microscopic motion of electrons. You will master the definition of electric current as the rate of charge flow, the concept of current density and drift speed, and the distinction between conventional current direction and actual electron motion. These ideas form the bedrock on which every later chapter is built.

Concept Overviews

4 Lessons

1:43:10

Problem Walkthroughs

5 Lessons

1:12:12

2. Resistance and Resistivity

This chapter explains why different materials allow current to flow more or less easily. You will learn the precise definitions of resistance and resistivity, how they relate to the physical dimensions of a conductor, and how temperature affects a material's ability to conduct. You will master the calculation of resistance from resistivity, length, and cross-sectional area; the distinction between ohmic and non-ohmic materials; and the temperature coefficient of resistivity. These skills let you predict how a real wire or component will behave under different conditions.

Concept Overviews

3 Lessons

Problem Walkthroughs

4 Lessons

3. Ohm's Law

This chapter unpacks Ohm's law from both a macroscopic and a microscopic perspective. You will learn what it truly means for a device or material to obey Ohm's law, and why metals satisfy this condition through the free-electron model of conduction. You will master the derivation of resistivity in terms of electron mass, charge, number density, and mean free time; the calculation of mean free time and mean free path; and the identification of conditions under which Ohm's law breaks down. These insights connect the circuit-level behaviour you have studied to the atomic-scale physics of metals.

Concept Overviews

4 Lessons

Problem Walkthroughs

3 Lessons

4. Electrical Power

This chapter explains how electrical energy is transferred and dissipated in circuits. You will learn to calculate the power delivered by a source, the power dissipated in a resistor, and the power absorbed when a battery is being charged. You will master the three equivalent forms of the power equation for resistive dissipation, the distinction between general power transfer and resistive dissipation, and the application of energy conservation to complete circuits. These skills are essential for selecting components that will not overheat and for understanding the efficiency of real power systems.

Concept Overviews

4 Lessons

Problem Walkthroughs

4 Lessons

5. Electromotive Force

This chapter introduces the concept of electromotive force and explains how real batteries differ from ideal ones. You will learn the definitions of emf, terminal voltage, and internal resistance, and how to apply the loop rule to single-loop circuits containing real batteries. You will master the calculation of current in a single-loop circuit with internal resistance, the determination of terminal voltage under load, and the analysis of circuits with multiple real batteries. These skills let you predict the actual voltage available to an external circuit and understand why a battery's terminal voltage drops when current flows.

Concept Overviews

3 Lessons

Problem Walkthroughs

5 Lessons

6. Resistors in Series

This chapter explains how resistors behave when connected end-to-end in a single current path. You will learn why the current is the same through each resistor in series, how to calculate the equivalent resistance, and how the total potential difference divides across the individual resistors. You will master the derivation of the series equivalent resistance formula, the calculation of current and voltage drops in series circuits, and the identification of series combinations within larger networks. These skills form the first half of the toolkit for reducing complex circuits to simple equivalent forms.

Concept Overviews

3 Lessons

Problem Walkthroughs

3 Lessons

7. Resistors in Parallel

This chapter explains how resistors behave when connected across the same two points, providing alternative current paths. You will learn why the potential difference is the same across each resistor in parallel, how to calculate the equivalent resistance, and how the total current divides among the branches. You will master the derivation of the parallel equivalent resistance formula, the calculation of branch currents using the current divider principle, and the step-by-step reduction of mixed series-parallel networks. Together with Chapter 6, these skills let you solve any circuit that can be reduced to simple equivalent resistances.

Concept Overviews

3 Lessons

Problem Walkthroughs

6 Lessons

8. Kirchhoff's Rules

This chapter introduces the two fundamental rules that allow you to analyse any DC circuit, no matter how complex. You will learn Kirchhoff's junction rule based on conservation of charge and the loop rule based on conservation of energy, and how to apply them systematically to find unknown currents and potential differences. You will master the assignment of current directions and sign conventions for loop traversal, the construction of independent loop and junction equations, and the solution of simultaneous equations for multiloop circuits. These skills are the capstone of DC circuit analysis and let you solve bridge circuits and other networks that cannot be reduced by series-parallel methods.

Concept Overviews

4 Lessons

Problem Walkthroughs

3 Lessons

9. RC Circuits

This chapter extends DC circuit analysis to time-varying currents by introducing resistor-capacitor circuits. You will learn how a capacitor charges and discharges through a resistor, and how the charge, current, and voltage change exponentially with time. You will master the derivation of the charging and discharging equations, the calculation of the capacitive time constant, and the determination of charge and current at any time during the transient process. These skills are essential for understanding timing circuits, filters, and any application where currents change with time.

Concept Overviews

4 Lessons

Problem Walkthroughs

7 Lessons

10. Conclusion

This chapter reviews the complete body of knowledge you have built across the course, from the definition of current to the analysis of time-varying RC circuits. You will consolidate your understanding of how Ohm's law, Kirchhoff's rules, and equivalent resistance methods work together to solve any DC circuit problem. You will revisit the key formulae for current, resistance, power, emf, series and parallel combinations, and transient analysis, and see how they connect to the broader syllabus topics of magnetic fields and alternating currents that follow in subsequent courses.

Concept Overviews

1 Lesson