Linear Circuits 1 - 04 - Power

Name: Linear Circuits 1 - 04 - Power
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How Do You Calculate Electrical Power Absorbed and Generated in a Circuit?

Created byMark Budnik, Mark M. Budnik

Last updated 8/2020

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What you'll learn

What is electrical power?
How do you calculate electrical power?
What is the difference between electrical power absorption vs. generation?

Course content

1 section • 10 lectures • 35m total length

Introduction0:11
A Word on Linear Circuit Textbooks....0:19
What Is Power?3:47
Rewriting the Power Equation2:48
Rewrite power equation to distinguish absorbed from generated power in circuits, using P = V I with delta V and current into the positive terminal for loads, motors, and lights.
A First Example4:42
Ground at 0 V, a -1 V source and a 4 V source establish 3 V across a 470 ohm resistor; Ohm's law gives 6.38 mA.
Power Equations that Only Only ONLY Work for Resistors2:13
Explore power equations and Ohm's law, deriving P = I^2 R and P = V^2 / R from V = IR, noting these formulas apply only to resistors, not sources.
Summary1:38
Explore power in circuits, its unit the watt, equal to one joule per second, and the universal p = v i form, with p = i^2 r for resistors only.
An Example with a Source Absorbing Power9:52
Explore a two-source circuit where one battery generates power and the other absorbs it, linked by a low-resistance cable. Use Ohm's law to compute current and verify power balance.
An Example with a Current Source5:10
Analyze a current source circuit with a 10 ohm resistor, showing 40 W absorbed by the resistor and 40 W generated by the source, ensuring power sums to zero.
An Example with an Electrical Model of a Flashlight5:10
Compute power in a circuit with a 10-ohm resistor and a 2-amp current source, yielding a 20-volt drop and 40 watts absorbed, then verify by power balance.

Requirements

High School or College Physics
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Description

Day 4 of Linear Circuits. Students are introduced to electrical power. Many students will already be familiar with the equation P = V I. We rewrite this equation to make it easier to use and provide you with lots and lots of examples.

The material covers all of the lecture material from a fourth lecture in a traditional, sophomore-level linear circuits class.

Who this course is for:

Beginner Engineering and Physics Students