Unit 4: Electricity for Everyone

Essential Questions What is electricity and how is it measured? How do generators work? How is energy converted from one form to another? What are parallel and series circuits? What is a load limit, and how is it calculated? What does electricity cost?

Chapter Challenge For this unit’s chapter challenge, you will be using the scenario on page This is what your final exam will be in December A rubric will be given to you beforehand, so you know the criteria you will be assessed on You may prepare for the chapter challenge, but you can not bring any of your written work to the exam, only your textbook and rubric

Day 1: Generate (60 minutes) Learning Objectives To understand how energy is transformed Develop a personal model for electricity

Starter What are different ways that you use electricity in your daily life? Is there any “free” electricity available? Why pay for it if it is free? Time: 10 minutes

Activity 1 Watch the following video and think of the following: How would the light bulb not light? What are the effects of changing the speed or direction of cranking the generator? Time:

Activity 2 You will be given a number which represents the group you are in You will research with your group and present what you find in a particular way 1.Powerpoint 2.Poster 3.Poem/Story/Comic strip

What to research? What is a generator? How does it work? What are the different types of generators? How is energy transformed using a generator? Time: 40 minutes Presentations – next class

Closing and Homework Physics to Go, pg. 449 #2, 3, 4, 6

Day 2: Lighten Up Learning Objectives: Qualitatively describe current, resistance and voltage Define coulomb, ampere, volt Compare series and parallel circuits Recognize generator output load Extend your personal model of electricity

Starter Lights were the first electric appliances for the home How do light bulbs work? How does the electricity that makes the light bulbs glow work? Time: 15 minutes

Activity 1 Present your information that you researched about generators Time: minutes

Activity 2 Draw 2 diagrams of a circuit, one in series and one in parallel. They should have 3 light bulbs Battery What are the pros and cons of each type of circuit? Time: 10 minutes

Activity 3 Set up your circuits, one at a time Measure the voltage using the voltmeter to see if there are any differences in voltage in the two different circuits Check the voltage at various points in the circuit Write down your findings Time: 30 minutes

Activity 4 Discuss the following questions: What is resistance, current, and voltage? Where is there more current and voltage – in a series circuit or parallel circuit? Will electricity continue to flow if the circuit is broken in a parallel circuit? A series circuit? Why or why not? Use a diagram to help explain. Time: 20 minutes

Closing and Homework Read “For you to Read”, pg. 452 Physics to go, pg. 454 #1 What is resistance, current, and voltage? Where is there more current and voltage – in a series circuit or parallel circuit? Will electricity continue to flow if the circuit is broken in a parallel circuit? A series circuit? Why or why not? Use a diagram to help explain. Vocabulary list: Volt Ampere Coulomb Resistance Current

Day 3: Ohm’s Law Learning Objectives Calculate the resistance of an unknown resistor given the potential drop and current Construct a series circuit Properly use a voltmeter and ammeter in a series circuit Graph the relationship between voltage and current for a resistor that obeys Ohm’s Law

Starter What determines the brightness of a light bulb? How can a dimmer switch make the same light bulb appear dim or bright? What is resistance, current, and voltage? Where is there more current and voltage – in a series circuit or parallel circuit? Will electricity continue to flow if the circuit is broken in a parallel circuit? A series circuit? Why or why not? Use a diagram to help explain. Time: 15 minutes

Activity 1 Read through rules on pg Connect various resistors from the box to the battery source Measure the voltage and current for the different resistors What happens if you have more than 1 resistor? Record your data Time: 30 minutes

Activity 2 Graph the following data. What will be on the x- and y-axes? What does the slope represent? Time: 20 minutes Resistor value ( Ω ) Voltage (V)Current (A)

Activity 3 What is the relationship between resistance, voltage and current? Try to write an equation that represents the relationship Think: how do you calculate slope? Time: 5 minutes

Activity 4 Ohm’s Law Calculations: Example: Calculate the resistance in Ohms of a 9V battery that carries a current of 3A. Complete the calculations questions Time: 20 minutes

Closing and Homework Read the “For you to read” on pg. 459 Ohm’s Law Calculations Physics to go, #1, 3, 4

Day 4: Load Limit Learning Objectives: Define watt, insulator, and conductor Apply P = IV Measure the power limit of a 120-V household circuit Differentiate between a fuse and a circuit breaker Understand the need for circuit breakers and fuses in a home

Starter You have heard the term “blown a fuse” or “tripped” a circuit breaker What is a fuse? What is a circuit breaker? What conditions do you think make a fuse “blow” or a circuit breaker “trip”? Time: 15 minutes

Activity 1 How do we calculate the load limit? This will help you in your chapter challenge Homes for Everyone dwelling Power = Current x Voltage (P = IV), where power is measured in watts (W) Suppose you have 40 60W light bulbs plugged into a 120V circuit. What is the current flowing through the circuit? When a 41 st light bulb is plugged in, the circuit blows. What is the load limit of the circuit? How many 100W light bulbs could be plugged into this circuit? Time: 20 minutes

Activity 2 Determine the load limit of 1 1.5V battery Determine the load limit of 2 1.5V batteries (To do this, you must determine the current going through the circuit) See how many light bulbs you can hook up to try to determine the wattage of the light bulbs Time: 30 minutes

Activity 3 Complete the sample equations. Formulas are on next slide Time: 20 minutes

Homework What are power, current, voltage, and resistance and how are they calculated? What is a circuit breaker and a fuse? Read Physics Talk Physics to Go, pg. 469 #1, 2 (note the voltage difference here, we do not use 120V, unless the appliance is from North America), 3, 4, 5, 10, 11

Day 5: Who’s in Control (60 minutes) Learning Objectives: Explain how a variety of automatic electrical switches work Select switches and control devices to meet particular needs Insert a switch in a parallel circuit to control a particular lamp

Starter Many electrical switches are operated manually, and many others are automatic List as many different kinds of automatic switching devices as you can What are the conditions that cause the on/off action of the switch? Time: 15 minutes

Activity 1 Create a circuit with 3 light bulbs in parallel Draw a corresponding diagram (pg. 473) Which alligator clip could be replaced with a switch in order to turn on and off all three bulbs? Make a diagram and test your prediction Which alligator clip could be replaced with a switch if you wanted to turn the furthest bulb on and off? Make a diagram and test your prediction Repeat for the middle bulb, and the closest bulb to the battery Time: 35 minutes

Activity 2 Share your diagrams and conclusions with a person from another group Discuss any discrepancies you have in your data Time: 5 minutes

Homework Read Physics Talk, pg. 475 Physics to go, pg. 483 #2, 3, 4, 6, 7, 9

Day 6: Cold Shower Learning Objectives: Calculate the heat gained by a sample of water Calculate the electrical energy dissipated by a resistor Recognize and quantify an ideal mechanical/electrical equivalent of heat Calculate the efficiency of a transformation of electrical energy to heat Explore the power ratings and energy consumption levels of a variety of electrical appliances

Starter The entire daily energy output of a Homes For Everyone (HFE) generator would not be enough to heat water for an average American family for a day. If an electrical heating coil (a type of resistor) were submerged in a container of water, and if a current were to flow through the coil to make it hot, what factors would affect the temperature increase of the water? Predict how each factor affects the water temperature. Time: 15 minutes

Activity 1 Before we begin our data collection, there are some formulas we need to understand Q = mc Δ T, where Q = Heat energy, m = mass, c = specific heat of material, Δ T = change in temperature P = E/t, where P = power, E = energy, t = time (E=Pt) Calculate the heat energy for a 0.5kg sample of water that went from 20°C to 45°C. The specific heat for water is 4.180J/kg°C. What was the energy input needed to heat the water sample if 1500W of power were used and it took 120s to heat the water? Time: 20 minutes

Activity 2 You will heat up a 100g sample of water Complete the table on pg. 487 We will not use a calorimeter, just a hotplate and a beaker Have the hotplate going for 5 minutes Repeat, this time using 250g of water Complete a 2 nd column for your table Time: 20 minutes

Activity 3 Calculate the Q and E values for each of your samples. Q = mc Δ T E = Pt You will have to get the power value from your hotplate Time: 10 minutes

Activity 4 Review rubric and assessment guidelines for chapter challenge Assign partners Time: 10 minutes

Homework Read Physics Talk, pg. 489 Physics to go, pg. 492, #1, 2, 3, 4, 5, 7, 8, 9

Day 7: Pay Up

Day 8: More for Your Money