19-1-ohms-law_summary

Ohm's law is a fundamental concept in electricity that explains the relationship between electric current (I), voltage (V), and resistance (R) in an electrical circuit. The learning objectives for this section include: 1. Describing how current is related to charge and time, distinguishing between direct current (DC) and alternating current (AC), and calculating current. 2. Defining resistance and describing Ohm's law (I = V/R). 3. Solving problems involving Ohm's law. Ohm's law states that the current through a conductor is directly proportional to the voltage (or potential difference) across it, and inversely proportional to the resistance. In equation form, this is expressed as I = V/R. Electric current is the rate at which electric charge flows, with units of amperes (A). The direction of conventional current is defined as the direction in which positive charges would flow, even though in most materials it is electrons that carry the current. Resistance is a measure of the opposition that a material offers to the flow of electric current. It is measured in units of ohms (Ω), or volts per ampere. Most materials follow Ohm's law, meaning that their resistance is independent of voltage in a wide range, and are called ohmic materials. Nonohmic materials, which do not follow Ohm's law, include semiconductors and some gas-filled devices like vacuum tubes and neon lamps. As industries grew, accurate measurement of current became increasingly important. In the late 19th century, Andre-Marie Ampere established the standard unit for electrical current, named after him, and modern electrical systems were developed based on Ohm's law. Today, electricity powers a wide range of devices and technologies, and understanding the principles of Ohm's law and electrical circuits is essential for many engineering and technological applications. The Snap Lab exercise "Vegetable Current" is an experiment demonstrating the concept of electric current by using peas flowing through a straw as a simple model.