### Unit 3: Electronic Circuit Theory

Although the study of electric and magnetic fields is interesting in and of itself, it may not seem directly useful in the real world. However, the interplay between these phenomena is responsible for much of the technology you see in your everyday life. For example, all electronics apply various features of electromagnetism, so that computers, HDTV, iMacs and iPads, smartphones, motors, fans, lights, and so on are applied electromagnetic devices. In this unit, we will take a quick look at the foundations of electronics, while at the same time adding to our understanding of electromagnetism.

**Completing this unit should take you approximately 8 hours.**

Upon successful completion of this unit, you will be able to:

- state Ohm's law in words;
- apply Ohm's law to simple circuits;
- calculate effective resistance of a network of resistors;
- determine the resistance of a cylindrical wire;
- compare and contrast voltage and current;
- use the junction and loop rules to analyze basic circuits;
- explain how a battery works; and
- calculate the power in a DC circuit.

### 3.1: Electric Current, Voltage and Resistance

Please watch these three lectures, pausing to take notes, before moving on to the reading below.

Please read the sections three through eight of "Chapter 21: Electricity and Circuits" carefully (PDF pages 566-608). Complete the Self Checks throughout the chapter (answers on page 981). Think about the Discussion Questions and Examples, and work out the problems ##10 – 12, ##16 – 17, and ##24 – 38. You can check some of the answers here.

Please read these sections: "Electric Circuits," "Ohm's Law," "Resistance and Resistivity," "EMF and Internal Resistance," and "Resistors in Series and in Parallel." Try worked Examples 7.1 and 7.2 before looking at the solution. Make sure you understand not only the solutions but how to approach solving the problems so that you can obtain the solutions yourself. You will be responsible for being able to solve problems of this type on the Final Exam.

Treat this demonstration as a laboratory experiment. Measure voltage, resistance, and current levels for a variety of conditions, and use Ohm's Law to explain the results. Think how the equivalent resistance of the circuit is compared to that of individual resistors' (less or greater?) and how this affects the resultant current.

Treat this demonstration as a laboratory experiment. Measure voltage, resistance, and current levels for a variety of conditions, and use Ohm's Law to explain the results. Think how the equivalent resistance of the circuit is compared to that of individual resistors' (less or greater?) and how this affects the resultant current. Which connection – series or parallel – should be used to produce maximum possible current?

### 3.2: Electric Circuits

Please watch these lectures, pausing to take notes, before moving on to the reading below.

Please read these sections: "Kirchhoff's Rules," "Capacitors in DC Circuits," "Energy in DC Circuits," and "Power and Internal Resistance." Try worked examples 7.3 and 7.4 before looking at the solution. Make sure you understand not only the solutions but also how to approach solving the problems so that you can obtain the solutions yourself. You will be responsible for being able to solve problems of this type on the Final Exam.

Treat this demonstration as a laboratory project in which you calculate the resistance expected for a given network before "measuring" the actual resistance using the demonstration. Use this worksheet as a guide to derive the general formula for the equivalent resistance of the given network.

This demonstration illustrates how a current indicating meter (the galvanometer) can be used in simple circuits to measure voltage, current, or resistance over a wide range of values. Despite the text appended to the demonstration, there is no way to vary the circuit elements of the multimeter, and we are not supplied with the actual values used in the demonstration. However, the three selectable modes of operation all make simple application of Ohm's Law, so see if you can understand the operation of the multimeter based on Ohm's Law and the indicated circuits.

### Unit 3 Assessment

Take this assessment to check your understanding of the materials presented in this unit.

**Notes:****There is no minimum required score to pass this assessment, and your score on this assessment**__will not__factor into your overall course grade.**This assessment is designed to prepare you for the Final Exam that will determine your course grade. Upon submission of your assessment you will be provided with the correct answers and/or other feedback meant to help in your understanding of the topics being assessed.****You may attempt this assessment as many times as needed, whenever you would like.**