Science Lesson Plan 1 Electricity Audit

By Darwin Daugaard

Unit Title: Electricity

Big Idea: Introduction to electricity, ohm’s law and power.

Topic/nature of the Investigation:

Energy Audits of Household AppliancesThe objective of this activity is to determine the amount of electrical energy that is required to operate certain household electronic devices.

Knowledge Learning Objectives:

The students will be able to define ohm’s law and calculate voltage, amps or resistance in simple circuits. They will also be able to define power and calculate the power of a simple circuit.

Skill and Reasoning Learning Objectives

The students should be able to calculate power and relate the measurements made in lab to problems involving ohm’s law and power.

Duration: 4-90 minute blocks

Context Issues of the Lesson

Planning Stages Within the 5-E Inquiry Model

Engage

PURPOSE:to convey the context of the lesson(s)/unit by conveying an important Key Questionto engage students in investigations that reveal their thinking to themselves and the teacherto record the initial ideas of students to engage their interest

Key Question: How are voltage, resistance and current related?Opening activity to surface student thinking:1.) Have the students take a look at a simple circuit (flash light).Opening activity to engage student interest and/or clarify context of the investigations:2.) Do the “energy audit” activity.Questions for whole group discussion:How much power do different devices consume? How do you calculate voltage, amps and power?

Explore

PURPOSE:to test ideas and develop knowledge using explorations, investigations, experimentsto modify and record ideas as they change due to activitiesto develop new questions and testable hypotheses

Activities (list) Driving Question

3.) Put together a simple circuit. What are the requirements for a circuit to work?How might a person change a circuit to change its power consumption?

Student Communication Product: (written report, oral presentation, poster, etc.)(consider showing “Models” of student products to help student identify characteristics of quality)

Have the students talk in their groups and explain to each other the requirements of a circuit and how power could be or not be affected by changes in the circuit.

Explain

PURPOSE:to answer the Key Question through student explanationsto provide students with relevant vocabulary, formal definitions and explanations of concepts

Content Media: (written material, video, teacher lecture, technology)Show a power point over electricity.Clarifying Questions for Whole/Small Group Discourse:Do all objects that plug into the 110 circuit take the same power?Student Communication Product (assessment): (unit test, written report, oral presentation, poster, etc.)

Elaborate

PURPOSE:to extend students' conceptual understanding through application or practice in new settings

Activities:4.) Do the activity “Energy Audits of Household Appliances”.5.) Students will also do the Activity on the “Home Energy Audit.”Content Media: (written material, video, teacher lecture, technology)Lecture showing the students how to calculate power from measuring voltage, current and resistance of an object.Extending/Application Questions for Whole/Small Group Discourse:Discuss how different objects may require the same or different power when used.Student Communication Product (assessment): (unit test, written report, oral presentation, poster, etc.)6.) The students will do the Audit Assessment.

Evaluate

PURPOSE:for students to assess their understand of the learning objectivesfor the teacher to assess student understanding of the learning objectives

Skill/Reasoning Learning Objectives Assessment Instrument

The students should be able to calculate power and relate the measurements made in lab to problems involving ohm’s law and power.

The students will answer questions on a quiz and test. The students will also do some calculation problems on the test.Worksheets and book questions.

Knowledge Learning Objectives Assessment Instrument

The students will be able to define ohm’s law and calculate voltage, amps or resistance in simple circuits. They will also be able to define power and calculate the power of a simple circuit.

The students will describe how to calculate the power and explain why some objects are different from each other based on power consumption.Worksheets and book problems.

HS-ETS-ED Engineering Designa. We can have the students ask and collect data on energy consumption to find evidence of machines that utilize large amounts of energy.b. Higher level classes could propose methods of reducing energy consumption based on energy audit.c. Nod. Noe. Nof. NoHS – ETS-ETSS Links Among Engineering, Technology, Science, and SocietyA. Students utilize the energy audit to plan how they may reduce energy consumption.B. NoC. Students could look at a specific device to determine what device is most energy efficient. They could compare this to energy star rates to make comparison and come up with suggestions.D. High level groups could look into comparing the price to change from one device to another. For instance, purchase of new appliance when old appliance is still functional.

Current and Voltage Difference

• The net movement of electric charges in a single direction is an electric current.

• When an electric current flows in the wire, electrons move randomly movement, but they also drift in the direction that the current flows.

• Electric current is measured in amperes.

Voltage Difference • In some ways, the electric force that causes

charges to flow is similar to the force acting on the water in a pipe.

• Water flows from higher pressure to lower pressure.

Voltage Difference

• In a similar way, electric charge flows from higher voltage to lower voltage.

• A voltage difference is related to the force that causes electric charges to flow. Voltage difference is measured in volts.

Electric Circuits • A closed path that electric current follows is

a circuit. • If the circuit is broken current will not

flow.

Batteries • To keep an electric current continually

flowing in the electric circuit a voltage difference needs to be maintained in the circuit.

• A battery can provide the voltage difference that is needed to keep current flowing in a circuit.

• Current flows as long as there is a closed path that connects one battery terminal to the other battery terminal.

Dry-Cell Batteries

• A cell consists of two electrodes surrounded by a material called an electrolyte.

• The electrolyte enables charges to move from one electrode to the other.

Dry-Cell Batteries • One electrode is the carbon rod, and the other

is the zinc container. • The electrolyte is a moist paste containing

several chemicals.

• The cell is called a dry cell because the electrolyte is a moist paste, and not a liquid solution.

Wet-Cell Batteries • A wet cell contains two connected plates

made of different metals or metallic compounds in a conducting solution.

• A wet-cell battery contains several wet cells connected together.

Lead-Acid Batteries

• Most car batteries are lead-acid batteries.

• A lead-acid battery contains a series of six wet cells made up of lead and lead dioxide plates in a sulfuric acid solution.

• The chemical reaction in each cell provides a voltage difference of about 2 V, giving a total voltage difference of 12 V.

Resistance • As the electrons flow through the filament in a

lightbulb, they bump into the metal atoms that make up the filament.

• In these collisions, some of the electrical energy of the electrons is converted into thermal energy.

• Eventually, the metal filament becomes hot enough to glow, producing radiant energy that can light up a dark room.

Resisting the Flow of Current

• Resistance is the tendency for a material to oppose the flow of electrons, changing electrical energy into thermal energy and light.

• Resistance is measured in ohms ().

• The resistance of a wire, or any conductor, increases as the wire becomes longer.

• The resistance also increases as the wire becomes thinner.

Temperature, Length, and Thickness

• The electric resistance of most materials usually increases as the temperature of the material increases.

The Current in a Simple Circuit • A simple electric circuit contains a source of

voltage difference, such as a battery, a device, such as a lightbulb, that has resistance, and conductors that connect the device to the battery terminals.

• When the wires are connected to the battery terminals, current flows in the closed path.

• The voltage difference, current, and resistance in a circuit are related.

Ohm's Law

• Ohm's law provides a way to measure the resistance of objects and materials. First the equation above is written as:

• According to Ohm's law, the current in a circuit equals the voltage difference divided by the resistance.

Question 1

A. An open circuit B. Electric currentC. Proton flowD. Voltage

__________ is the net movement of electric charges in a single direction.

The answer is B. Electric forces in a material cause electric current to flow.

AnswerA volt is the unit of measurement for voltage difference, which is related to the force that causes electric charges to flow.

Question 2

What is a volt?

Question 3What is the tendency for a material to oppose the flow of electrons called?

Answer

The tendency for a material to oppose the flow of electrons is called resistance, and is measured in ohms.

The students will be handed a flashlight and asked to put the batteries in them in both directions. They will be given time to discuss their results in their groups and then asked to share with the class.

Activity 1

Back to lesson plan.

Back to lesson plan.

Back to lesson.

The students will do an activity putting together a simple circuit, a series circuit and a parallel circuit.

Back to lesson.

Back to lesson.

Back to lesson.

Back to lesson.

Back to lesson.

ME Energy Audit AssessmentDetermine the amount of total money from using ten (10) of the following appliances for the time allotted for each for a thirty day month. All units will be in Watts (W). Calculate the kilowatt hours at a cost of $0.102 per kilowatt hourClock radio = 10 for 24 hoursCoffee maker = 900–1200 for 1 hourClothes washer = 350–500 for 2 hoursClothes dryer = 1800–5000 for 2 hoursDishwasher = 1800 for 2 hours (using the drying feature greatly increases energy consumption)Dehumidifier = 785 for 24 hoursFans

Ceiling = 120 for 10 hoursWindow = 150 for 10 hoursFurnace = 750 for

Hair dryer = 1550 for ½ hourClothes iron = 1400 for ½ hourMicrowave oven = 925 for 1 hourPersonal computer

Laptop = 50 for 12 hoursRadio (stereo) = 230 for 3 hoursRefrigerator (frost-free, 16 cubic feet) = 725 for 24 hoursTelevisions (color) pick one for 6 hours

19" = 65–11027" = 11336" = 13353"-61" Projection = 170 Flat screen = 120

Toaster = 1100 for ½ hourVCR/DVD = 20 for 1 hourVacuum cleaner = 1220 for 1 hourWater heater (40 gallon) = 5000 for 24 hours Back to lesson.

Physical Science Test C-Electricity1. A radio uses 3.5 X 10-3 A of current when it is operated by a 4.5 volt battery. What is the resistance of the radio circuit?2. A 23 ohm electric heater operates on a 120 volt outlet.

What is the current through the heater?How much energy is used by the heater in 40 seconds?How much thermal energy is given off in this amount of time?

3. Three 30 ohm resisters are connected in series across a 120 volt generator. What is the equivalent resistance in the circuit?

What is the current in the circuit?4. Three 30 ohm resisters are connected in parallel across a 120 volt generator. What is the equivalent resistance in the circuit?

What is the current in the circuit?5. TJ’s lovely PS-2 has a resistance of 134 ohms and is plugged into a 120 volt outlet.

How much current does it draw?How much power does it use?If TJ’s dad pays 27 cents per KWh how much does it cost to run the PS-2 for 4 hours a day for a 30 day period?

Lesson Plan

Resources

1. Lesson Plan template- found one on the web and changed it.

2. Power point from Glencoe Physical Science 1995.

1. Lesson Plan template- found one on the web and changed it.

6. Lesson Plan template- found one on the web and changed it.

3. The Easy Energy Action Plan – LoseYourExcuse.com

4. Energy Audit of Household Appliances-Engineering the future Workshop.

5. Home Energy Audit- Coolschoolchallenge.org