Voltage

An in-depth explanation of the fundamental concept of voltage. Covers voltage polarity, ground, and voltage measurement. A Test Your Knowledge! section is included to enhance the learning process.

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Measuring Voltage Using Digital Multimeters

Detailed instructions on how to measure voltage using a digital multimeter. This topic page also explains the several different settings on a DMM. Includes a Test Your Knowledge! section to practice the material covered.

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Ideal Independent Voltage and Current Sources

Circuit elements are commonly categorized as either passive or active. A circuit element is passive if the total amount of energy it delivers to the rest of the circuit (over all time) is non-positive. (Passive elements can temporarily deliver energy to a circuit, but only if the energy was previously stored in the passive element by the circuit.) An active circuit element has the ability to create and provide power to a circuit from mechanisms external to the circuit.

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Interactions Between Electrical and Nonelectrical Systems

An electrical system is often used to drive a non-electrical system (in an electric stove, for example, electric energy is converted to heat). Interactions between electrical and non-electrical systems are often described in terms of power. Electrical power associated with a particular circuit element is the product of the current passing through the element and the voltage difference across the element.

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Kirchhoff's Voltage Law

Understanding Loops in a Circuit

KVL depends upon the concept of a loop. A loop is any closed path through the circuit which encounters no node more than once. Essentially, to create a loop, start at any node in the circuit and trace a path through the circuit until you get back to your original node.

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Source Voltages Greater Than 5V

Design Challenge, Problem 1

This exercise uses concepts introduced in our experiment relative to implementing circuits with multiple sources that are greater than 5V.

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Voltage Dividers

Project 4: Resistors

If the total voltage difference across a set of series resistors is known, the voltage differences across any individual resistor can be determined by the concept of voltage division.

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Ohm's Law

Ohm's Law states that the voltage difference across a resistor is proportional to the current through the resistor. This topic page will guide the user through a set of problems to help understand how to apply Ohm's Law.

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Voltage-Current Characteristics

In any electric circuit, our typical goal is to move charges around to perform some useful task. This involves both voltage differences and currents. We create voltage differences in the circuit, which provides energy differences (or electromotive forces) which move charges around, creating currents.

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Series Resistors

Voltage Dividers

If the total voltage difference across a set of series resistors is known, there is an easy way to determine the voltage across any individual resistor in the series combination. The appropriate formula is called the voltage divider formula, since the total voltage is divided among the individual resistors.

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Resistors

Voltage-Current Characteristics and Nonlinearities

In this section, we will look at Ohm's law from the standpoint of a voltage-current relationship. This will provide some continuity with our presentation of voltage current relationships for other components, such as capacitors, inductors, diodes, and transistors later on.

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Electrical Basics

Current and Voltage

This topic page covers background material relating to current and voltage.

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Ohm's Law

Design Challenge 4: Current-Limiting Resistor

Resistors in electrical circuits are commonly used to provide other components in the circuit with the voltages and currents they require in order to function properly. For example, in this exercise, we will design our circuit (i.e. choose a resistance value) to ensure that an LED receives the voltage necessary for it to light up without allowing excessive current, which could burn out the LED.

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Ohm's Law

Design Challenge 5: Inferring Current From Voltage

Measuring current directly tends to be tedious—you generally need to break open your circuit in order to insert the ammeter into the circuit. Voltage measurements tend to be considerably easier, so it is common to determine the current in a circuit by measuring the voltage across a known resistor and using Ohm's law to estimate the current through the resistor.

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Voltage Dividers

Design Challenge 1: Series Resistors

In this design challenge, we will build a circuit with a 5V source, 6.8 kΩ, and an arbitrary resistor. We will use the concept of voltage division to determine the resistance value of the arbitrary resistor when given a specific voltage drop across it.

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Voltage Dividers

Design Challenge 2: Controlling Current

Voltage dividers and resistors in series can also be used to control the amount of current that is drawn from a power source.

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Voltage Dividers

Design Challenge 1: Temperature Measurement

Design a circuit whose output voltage provides a crude temperature measurement.

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