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Investigation Ohm's Law for Ohmic and Nonohmic Conductors

Overview

Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA

This experiment investigates Ohm's law, which relates current, voltage, and resistance.

One goal of the experiment is to become familiar with circuit diagrams and the terminology involved in basic circuits, such as resistor, resistance, current, voltage, and power supply. By the end of the experiment, familiarity is gained with how to wire up a circuit and how to measure both the current passing through a circuit component and the potential difference, or voltage, across it.

In a circuit, a battery or power supply provides a voltage measured in volts (V) that makes the charge flow. Other elements in the circuit, such as light bulbs or resistors (which are often just long narrow wires wound into coils) limit the rate at which the charge flows. The rate of flow of the charge is known as current measured in amperes (A), or amps for short, and the degree to which resistors and light bulb filaments limit the flow is known as their resistance measured in ohms (Ω). This experiment involves an exploration of Ohm's law, which relates voltage, current, and resistance.

This experiment also explores the difference between a basic circuit component called a resistor, and a light bulb and a light-emitting diode (LED). Light bulbs and LEDs are part of many common devices and are used for various lighting applications, and so it is useful to understand how they work.

Procedure

1. Becoming Familiar with the Apparatus

  1. For this experiment, use a computer to collect the data and plot graphs.
  2. Load the software for the experiment by double-clicking on the "Ohm's Law" icon on the computer desktop. When the program loads, the screen should show a graph, a table, and in the lower right corner, boxes with the voltage and current readings.
  3. Click the Zero button and select "Zero All Sensors" to make sure that the voltage and current readings read zero wh

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Application and Summary

Electronic gadgets are omnipresent in today's world, and Ohm's law has a role to play in each of these gadgets. For instance, a flashlight designed to work on two 1.5-volt batteries in series (a total of 3 volts), must have a light bulb with an appropriate resistance, so that the batteries provide an appropriate amount of current to allow the bulb shine brightly, without burning out. Ohm's law helps guide that choice of bulb.

Another application is a three-way light bulb, which can shine with

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