Learn about the physics of resistance in a wire. Change its resistivity, length, and area to see how they affect the wire's resistance. The sizes of the symbols in the equation change along with the diagram of a wire.

Ohm’s Law is V = IR, where V = voltage, I = current, and R = resistance. Ohm’s Law allows you to determine characteristics of a circuit, such as how much current is flowing through it, if you know the voltage of the battery in the circuit and how much resistance is in the circuit. Created by Sal Khan.

How to calculate the current through a resistor in parallel using equivalent resistance and Ohm's law.

In this video David quickly explains each charge and circuit concept and does a sample question for each one. Created by David SantoPietro.

Traditionally, progress in electronics has been driven by miniaturization. But as electronic devices approach the molecular scale, classical models for device behavior must be abandoned. To prepare for the next generation of electronic devices, this class teaches the theory of current, voltage and resistance from atoms up. To describe electrons at the nanoscale, we will begin with an introduction to the principles of quantum mechanics, including quantization, the wave-particle duality, wavefunctions and Schrödinger’s equation. Then we will consider the electronic properties of molecules, carbon nanotubes and crystals, including energy band formation and the origin of metals, insulators and semiconductors. Electron conduction will be taught beginning with ballistic transport and concluding with a derivation of Ohm’s law. We will then compare ballistic to bulk MOSFETs. The class will conclude with a discussion of possible fundamental limits to computation.

This module covers fundamental DC circuit principles to help post-secondary electrical engineering technology students understand basic concepts and perform limited circuit analysis. 

The lesson will first explore the concept of current in electrical circuits. Current will be defined as the flow of electrons. Photovoltaic (PV) cell properties will then be introduced. Generally constructed of silicon, photovoltaic cells contain a large number of electrons BUT they can be thought of as "frozen" in their natural state. A source of energy is required to "free" these electrons if we wish to create current. Light from the sun provides this energy. This will lead to the principle of "Conservation of Energy." Finally, with a basic understanding of the circuits through Ohm's law, students will see how the energy from the sun can be used to power everyday items, including vehicles. This lesson utilizes the engineering design activity of building a solar car to help students learn these concepts.

Students are introduced to several key concepts of electronic circuits. They learn about some of the physics behind circuits, the key components in a circuit and their pervasiveness in our homes and everyday lives. Students learn about Ohm's Law and how it is used to analyze circuits.

See how the equation form of Ohm's law relates to a simple circuit. Adjust the voltage and resistance, and see the current change according to Ohm's law. The sizes of the symbols in the equation change to match the circuit diagram.

In this extension to the Ohm's Law I activity, students observe just how much time it takes to use up the "juice" in a battery, and if it is better to use batteries in series or parallel. This extension is suitable as a teacher demonstration and may be started before students begin work on the Ohm's Law I activity.

We are surrounded everyday by circuits that utilize "in parallel" and "in series" circuitry. Complicated circuits designed by engineers are made of many simpler parallel and series circuits. In this hands-on activity, students build parallel circuits, exploring how they function and their unique features.

Does the real-world application of science depend on mathematics? In this activity, students answer this question as they experience a real-world application of systems of equations. Given a system of linear equations that mathematically models a specific circuit—students start by solving a system of three equations for the currents. After becoming familiar with the parts of a breadboard, groups use a breadboard, resistors and jumper wires to each build the same (physical) electric circuit from the provided circuit diagram. Then they use voltmeters to measure the current flow across each resistor and calculate the current using Ohm’s law. They compare the mathematically derived current values to the measured values, and calculate the percentage difference of their results. This leads students to conclude that real-world applications of science do indeed depend on mathematics! Students make posters to communicate their results and conclusions. A pre/post-activity quiz and student worksheet are provided. Adjustable for math- or science-focused classrooms.

This is a YouTube video that brings out the main concepts in chapter 20 of the college physics text book. The chapter is on Electric Currents and Resistance.