Unit 4: Electricity for Everyone. Essential Questions What is electricity and how is it measured?...

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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 444-445

• 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?

• 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?

Activity 1

• Present your information that you researched about generators

• Time: 15-30 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?

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

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.

• 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.

Activity 1

• Read through rules on pg. 456-457

• 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

Activity 2

• Graph the following data. What will be on the x- and y-axes? What does the slope represent?

Resistor value (Ω)

Voltage (V) Current (A)

3 1.5 0.5

3 4.5 1.5

10 1.5 0.15

10 3 0.30

10 4.5 0.45

15 1.5 0.1

15 3 0.2

15 4.5 0.3

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

• 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”?

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 41st 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?

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

Activity 3

• Complete the sample equations.

• Formulas are on next slide

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?

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

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.

Activity 1

• Before we begin our data collection, there are some formulas we need to understand• Q = mcΔT, where Q = Heat energy, m = mass, c =

specific heat of material, ΔT = 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?

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 2nd column for your table

Activity 3

• Calculate the Q and E values for each of your samples.• Q = mcΔT• E = Pt

• You will have to get the power value from your hotplate

Activity 4

• Review rubric and assessment guidelines for chapter challenge

• Assign partners

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

Unit 4: Electricity for Everyone. Essential Questions What is electricity and how is it measured?...

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