Back To Course

AP Physics 1: Exam Prep12 chapters | 136 lessons

Watch short & fun videos
**Start Your Free Trial Today**

Start Your Free Trial To Continue Watching

As a member, you'll also get unlimited access to over 55,000 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.

Free 5-day trial
Your next lesson will play in
10 seconds

Lesson Transcript

Instructor:
*Yuanxin (Amy) Yang Alcocer*

Amy has a master's degree in secondary education and has taught math at a public charter high school.

In this video lesson, you will learn how to find the power in an electric circuit using either the voltage or the resistance in the circuit. See how this power translates into the energy we see at work in light bulbs and other electrical products.

We are surrounded by electric circuits. We define an **electric circuit** as a closed loop through which electricity freely flows. The lights in your room are all powered by electric circuits. Your television, the computer you are using to read this lesson, and even your cell phone are all powered by electric circuits. Yes, electric circuits are very common nowadays in our electricity-reliant society.

When you turn these electric circuits on, you can see their energy and power at work. When you flip the switch for the lights in your room, you see your lights get bright and begin to emit light. When you turn on your television, you see the screen on your television turn on, and you can see various television programs brought to you by your local television providers. When you turn on your computer, you see your monitor turn on, and then, you can use all kinds of computer programs on it. When you turn on your cell phone, you are able to make phone calls and write texts to your friends and family

Where does this power and energy come from? It comes either from batteries or from your electricity provider. Since we are dealing with electric circuits, we are also dealing with electric power. We define **electric power** as the rate at which a circuit uses electrical energy. Electrical energy is the charge that comes from a battery or from the power plant. There are two ways to calculate this power. We can use either the voltage or the resistance of a circuit.

To use the voltage of the circuit, we can use this formula to calculate the power:

*P* = *V* * *I*

We have that power is equal to the voltage of the circuit times the current I of the circuit. When our unit for voltage is volts (*V*) and the unit for current is amperes, or amps for short (*A*), then we have to multiply them together to get the watt (*W*), the standard unit of power. So, say we have two 2.5-volt batteries connected together to make 5 volts. If we send a current of 0.5 amperes through it, we get a power of:

*P* = 5 *V* * 0.5 *A* = 2.5 *W*

You can power a clock with 2.5 watts of power.

Another way you can calculate power is by using the amount of resistance in a circuit. You can actually convert the power formula with voltage into the power formula with resistance by using Ohm's Law, which tells you *V* = *I* * *R* (voltage equals current times resistance).

*P* = *V* * *I*

*P* = (* I* * *R* ) * *I*

*P* = *I*^2 * *R*

Or,

*P* = *V* * *I*

*P* = *V* * (*V* / *R* )

*P* = *V*^2 / *R*

If you are given the current and resistance, you can use *P* = *I*^2 * *R* to find your power. If you are given the voltage and the resistance, then you can use *P* = *V*^2 / *R* to find your power.

For example, say you are given that a certain electric circuit has a resistance of 1500 ohms with a current running through it of 5 amps. The power used by this circuit is then:

*P* = *I*^2 * *R* = ( 5*A* )^2 * 1500 ohms = 25 * 1500 = 37,500 *W* or 37.5 *kW*

This is almost enough to run a curling iron.

Now, say that you are given another electric circuit that is run with 120 Volts and a resistance of 192 ohms. You use *P* = *V*^2 / *R* to find the power this circuit uses. You get:

*P* = ( 120*V*)^2 / 192 Ohms = 14400 / 192 = 75 *W*

This is enough to power a sewing machine.

Let's review what we've learned. An **electric circuit** is a closed loop through which electricity freely flows. **Electric power** is the rate at which a circuit uses electrical energy. The formula to find the power in a circuit is:

*P* = *V* * *I*

We use Ohm's Law (*V* = *I* * *R*) to derive two other power formulas that use the resistance of a circuit.

*P* = *V* * *I*

*P* = ( *I* * *R* ) * *I*

*P* = *I*^2 * *R*

Or,

*P* = *V* * *I*

*P* = *V* * ( *V* / *R* )

*P* = *V*^2 / *R*

To unlock this lesson you must be a Study.com Member.

Create
your account

Already a member? Log In

BackDid you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2,000 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

You are viewing lesson
Lesson
4 in chapter 11 of the course:

Back To Course

AP Physics 1: Exam Prep12 chapters | 136 lessons

- What is Electric Current? - Definition, Unit & Types 7:59
- Electrical Resistance: Definition, Unit & Variables 7:52
- Ohm's Law: Definition & Relationship Between Voltage, Current & Resistance 7:17
- Calculating Energy & Power in Electric Circuits 4:58
- Series Circuits: Definition & Concepts 9:01
- Parallel Circuits: Definition & Concepts 6:43
- Electric Circuit Diagrams: Applications & Examples
- Finding the Equivalent Resistance: Series, Parallel & Combination Circuits 6:35
- Applying Kirchhoff's Rules: Examples & Problems 7:29
- Go to AP Physics 1: Direct Current Circuits

- GACE Business Education Test II: Practice & Study Guide
- GACE Business Education Test I: Practice & Study Guide
- GACE Program Admission Combined Test I, II & III: Practice & Study Guide
- GACE Behavioral Science Test I: Practice & Study Guide
- GACE Health Education Test I: Practice & Study Guide
- Reading Comprehension Strategies for Literature
- Tools for Increasing Student Reading Comprehension
- Interdependence of Reading & Writing
- Basic Principles of Early Literacy
- Reading Comprehension Strategies for Children
- Common Core State Standards in Ohio
- Resources for Assessing Export Risks
- Preview Personal Finance
- California School Emergency Planning & Safety Resources
- Popsicle Stick Bridge Lesson Plan
- California Code of Regulations for Schools
- WV Next Generation Standards for Math

- Implications of Choice Theory on Social Policy & Crime
- Endoplasmic Reticulum Lesson for Kids: Definition & Function
- Nucleolus Lesson for Kids
- Why Was the Boston Massacre Important? - Lesson for Kids
- Seizures & Autism: Cognitive, Social & Behavioral Impacts
- Don Quixote Chapter 5: Summary & Analysis
- Collaborative Care: Nursing in Team-Based Settings
- Teaching Self-Management Skills to SPED Students
- Quiz & Worksheet - Parenteral Administration of Drugs
- Quiz & Worksheet - Personification in Beowulf
- Quiz & Worksheet - The Piece of String Plot
- Pollution Story Comprehension Questions & Worksheet
- Quiz & Worksheet - Cardioselective vs. Non-cardioselective Beta Blockers
- Growth & Opportunity for Entrepreneurs Flashcards
- Understanding Customers as a New Business Flashcards

- Prentice Hall Geometry: Online Textbook Help
- Western Civilization Since 1648: Homework Help Resource
- Principles of Management: Certificate Program
- ILTS Social Science - Psychology: Test Practice and Study Guide
- UExcel Precalculus Algebra: Study Guide & Test Prep
- Campbell Biology Chapter 19: Viruses
- U.S. Political Parties, Voters & Electoral Process
- Quiz & Worksheet - European Expansion of 2000-2009
- Quiz & Worksheet - Supporting Ideas of a Speech
- Quiz & Worksheet - Binomial Probabilities Using Formulas Practice Problems
- Quiz & Worksheet - Steps for Binomial Experiments Problems

- Using the Law of Sines to Solve a Triangle
- Diabetes and Sexual Dysfunction
- The Masque of the Red Death Lesson Plan
- Best Study Abroad Programs
- Fairfield, CA Adult Education
- First Grade Word Walls: List & Activities
- Memoir Lesson Plan
- FTCE Biology 6-12: Passing Score
- How to Go to College for Free
- Common Core Resources for High School Teachers
- Industrial Revolution Lesson Plan
- How to Study for a Math Test in College

Browse by subject