 Vernier Software & Technology

# Power and Energy

## Introduction

People often use the words power and energy interchangeably, when in fact these two words mean very different things.

Imagine if people used the words "kilometers per hour" and "kilometers" interchangeably. That would be very confusing! It would sound like this: "How fast can you ride your bike?" "About 5 kilometers." This is basically what we are doing if we use power and energy to mean the same thing.

Power is a rate–just like meters per second, miles per hour, and gallons per minute are rates. Power is the rate at which energy is transferred or work is done. It can be calculated using the equation $\text{power} = \frac{\text{amount of work done}}{\text{how much time it takes}}$

The base unit of power is the watt (W), which is equal to one joule per second (1 W = 1 J/s).

We can think of energy, on the other hand, as a quantity–just like gallons and meters are quantities. Energy refers to the amount of energy transferred or work performed. The base unit of energy is the joule (J). You can calculate energy by rearranging the power expression in the following way: $\text{amount of work done} = \text{power} \times \text{how much time it takes}$

As an example, let’s say you leave a 12 W light bulb on for 10 seconds. Using the expression above, you can calculate the amount of work: $\text{12 W} \times \text{10 s} = \text{amount of work done}$ $\text{12}\frac{J}{s} \times \text{10 s} = \text{120 J}$

In the United States, a common unit of energy is the watt-hour (Wh) or kilowatt-hour (kWh). With small classroom wind turbines and solar panels, we sometimes use the unit "milliwatt-second" (mWs), which is equal to one thousandth (1/1000) of a joule and could also be called a millijoule.

In this experiment, you will explore power and energy. You will learn how power and energy are related to each other. You will use this knowledge and the data-collection software to measure the power and calculate the amount of electrical energy generated by a small wind turbine.

## Objectives

• Understand the difference between power and energy.
• Calculate the amount of electrical energy generated by a wind turbine during a time period.

## Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

### Option 2

You may also need an interface and software for data collection. What do I need for data collection?

## Renewable Energy with Vernier

See other experiments from the lab book.

 1 Renewable Energy: Why is it So Important? 2 What is Energy? 3 Project: Energy Audit 4 Voltage and Circuits 5 Current and Resistors 6 Mechanical Power 7 Generators 8 Exploring Wind Turbines 9 Effect of Load on Wind Turbine Output 10 Blade Variables and Power Output 11 Solidity 12 Turbine Efficiency 13 Power Curves 14 Power and Energy 15 Project: Maximum Energy Output 16 Project: Build a Wind Farm 17 Exploring Solar Panels 18A Effect of Load on Solar Panel Output 18B Fill Factor and IV Curve of a Solar Panel 19 Variables Affecting Solar Panel Output 20 Effect of Temperature on Solar Panel Output 21 Project: Build a Solar Charger 22 Exploring Passive Solar Heating 23 Variables Affecting Passive Solar Heating 24 Exploring Solar Collectors 25 Variables Affecting Solar Collectors 26 Project: Solar Cooker

### Experiment 14 from Renewable Energy with Vernier Lab Book #### Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.