Learning Targets: To work with electronic components and meters to build circuits, measure and monitor electric properties, and explain the interactions taking place in the systems.

 Humans have been aware of this force for many centuries.  Ancient man believed that electricity was some form of magic because they did not understand it.

 Today we know of only 4 forces: electromagnetism  Strong nuclear force  Weak nuclear force  Gravity

About 3,000 years ago, a Greek philosopher named Thales (Θαλής) noticed that when a piece of amber was rubbed with wool cloth, it would attract lightweight objects such as straw or feathers. Amber is a yellow-orange rock made of fossilized tree resin (similar to sap). The Greek name for amber is ‘elektron’, and is the origin of our word electricity.

Static Lightning

 AnBf Animal/Human Nervous Systems Bioelectricity (Electric Eel)

 Wall outlets (dangerous)  Batteries (safe for classroom experiments)  Generators/Coal & NuclearPowerplants  Solar Cells  Wind turbines  Hydroelectric plants

 Electricity is a naturally occurring form of energy.  It is a force that exists all around us.  Static electricity is  Current electricity is a movement of charge, and in most cases the particle carrying the charge is the electron.

 Can be used to do work.  Can be converted into other useful forms of energy including:  Light  Sound  Heat  Motion

Students will:  Discover how to create complete circuits and how to identify series, parallel, and short circuits.  Demonstrate that closed circuits allow current to flow and open circuits do not allow current to flow.  Create and compare intensity of light produced by lamps in series and parallel circuits.  Observe that a switch can turn a lamp on and off by completing a circuit or creating a short circuit.  Set up circuits described in schematic diagrams.  Demonstrate the different performance of lamps in series and in parallel.  Describe how short circuits create an electric pathway that bypasses the intended components.  Communicate circuit designs and components using a symbolic system called schematic diagrams.

 Is the study of the effects of electrons moving through a vacuum, a gas, or a material.  Putting obstacles in the path of a stream of electrons to see if we can make them do something interesting or useful.

 Smoke alarms  Portable radios

 To change electric energy into light, using a 9-V battery and an electric component called a lamp.

 Work with one partner – your team will be given a number.  One set of materials to share: 9-V battery with wires (leads), and one light bulb (lamp)  5 minutes

 Electricity from the battery can make the lamps produce light.  Electricity had to go in an unbroken pathway from one side of the battery, to the lamp and back to the other side of the battery.

 The two connectors on the battery are called terminals, the positive terminal and the negative terminal.

 Electricity flows in a pathway called a circuit.  If the circuit is closed, or complete, all the way from one terminal to the other, the electricity will flow and the lamp will glow.  If the circuit is open (broken) someplace, the electricity will not be able to flow, and the lamp will not glow.

 The flow of electricity is called current. Electric current is due to the movement of electricity, rather like a river current is due to the movement of water.

 The current that flows from a 9-V battery is called direct current.  Direct current flows in one direction only through the circuit.  Current flows from the negative terminal to the positive terminal of the battery.  The red wire (hot wire) is connected to the positive and the black wire is connected to the negative terminal.

 Each team will have its own set of components. You will keep them in a bag. You will be the only students to use your components, so keep track of them carefully.  Your bag will have your team’s number written on it. You will use only the bag of components with your team’s number. The component bags will be kept in the file.  At the beginning of each class, you will come here to get your components, and at the tend of each class you will inventory our components and put them away in the same place.  Right now you will have one lamp in your component bags, but soon you may have a dozen or more items.  Batteries will be shared with other class. These will not be kept in the component bags.

GOAL Students will: Explore, measure, and manipulate one of the two main attributes of electricity (voltage) and discover how voltage can be influenced by components in a circuit.

OBJECTIVES  Measure voltage drops using a digital voltmeter.  Conduct systematic investigations of resistors and lamps to discover how components affect voltage.  Discover that the sum of the voltage drops across the components in a series circuit equals the voltage at the source.  Calculate the percentage of voltage drop and percentage of resistance imposed by components in series circuits.  Explain voltage as a push that moves current through a circuit.  Explain the relationship between voltage drops and resistances of the components in a circuit.  Describe dynamics in terms of the three great truths of circuitry.  Explain that resistance imposed by a component and voltage drop across that component are proportional.

Measuring Voltage We have been finding out some things about electricity and what it does when it moves through circuits containing various components. Today we will start an investigation to find out what moves electricity through the circuit.

 Electricity is a flow of electrons. The flow of electrons is called current.  Electrons move when a force is applied to them.  The force moving the electrons is called voltage.  When you hear someone mention the voltage of an electricity source, they are talking about the amount of push available to move current through a circuit.

 See CD ROM – Explanation of Voltage in the Technical Manual, Voltage and Batteries section.

 The same meter used to measure resistance can be used to measure voltage.  Project the transparency called Voltmeter and introduce it.  Turn the rotary switch 3 clicks counterclockwise to the 20-V setting.  At this setting, the voltmeter can measure voltage between 0 and 20 V.  Voltage is ALWAYS measured with the current flowing through the circuit.  Do NOT move the switch on the meter to measure resistance while you are working with electrified circuits.

 The difference in the amount of voltage on the two sides of a component is what the voltmeter measures.  The voltmeter measures the amount of voltage “used” by a component.  The amount of voltage used by a component is its voltage drop.  We will always refer to the voltmeter reading as a voltage drop.

 Use your meters and other components, including the springboards and batteries to explore voltage.  How much voltage drop is available across the poles of your battery?  What is the voltage drop across a lamp connected directly to a battery?  When the lamp is in a series with a 75-Ω resistor?  With a 330- Ω resistor?

 What is the voltage drop across one, two, and three lamps? Compare the voltage reading of each lamp when they are in series and when they are in parallel.  10 min. free exploration

See the transparency called “Measuring Voltage Drops in 4 Circuits”.  Demonstrate:  Draw a schematic of the first circuit. This one had two 150- Ω resistors.  Measure the voltage drop across a component.  Write the voltage drop in a circle near the component symbol on the schematic.  Draw two lines from the sides of the circuit to the schematic showing where you placed the two probes, or simply write the voltage on a short line next to the component.

 See Lab Notebook p Find the components required. 2. Set up the circuits. 3. Measure the voltage drops in each circuit. 4. Record your measurements on the schematics of the circuits.

Report what you found out about voltage drops in your circuits.  The battery drops _____ volts.  The battery has the highest voltage drop.  The resistor has the second highest voltage drop.  The resistor doesn’t always drop the same amount of voltage.  The lamp drops more voltage when it is bright.  The switch doesn’t drop any voltage when it is closed, but it drops a lot of voltage when it is open.

 Voltage is what moves current through circuits.  Voltage is like a force – a push or a pull.  When the electricity is pushed through some components, like resistors and lamps, the amount of available push is reduced. We can measure how much the available push is reduced with a voltmeter.  The difference in the amount of voltage on the two sides of a component is what the voltmeter measures.  We call that reduction of voltage a voltage drop.

 Which components had the largest voltage drops? (battery & resistor)  Which components had the smallest voltage drop? (lamps)

 Hand in the “Measuring Voltage Drops in Four Circuits” sheet.  Return the components to your bags  Secure the battery leads.  Turn the multi-meter off.  Return all materials to the materials station.

The Resistance / Voltage Relationship Think – Write – Pair – Share: How do you explain the voltage drop across the lamp in a circuit. (4 min)

 Open your Lab Notebook to Resistor Investigation from Inv. 2.  Review: The greater the resistance in series with a lamp, the dimmer the lamp glows.

 Lab Notebook p. 12  Repeat the series of investigations with the resistors of various values ▪ 75 Ω ▪ 150 Ω ▪ 330 Ω ▪ 1000 Ω But this time, measure the voltage drops across the lamp and the resistor in each circuit.

 Add one additional resistor to your investigation: The resistor is black/black/black, or a theoretical resistor of 0 Ω  How could you make a resistor with 0 of resistance?  Use the copper wire from your component bag!  Get springboards, component bags, multi- meters. (15-20 min)

Resistor Code Resista nce (ohms) Lamp Brightness 3 Groups report the values for lamp voltage drop. (Use the median in the next column) Lamp Voltage Drop Resistor Voltage Drop bl/bl/bl0Very bright v/gr/bl75Bright br/gr/br150Medium or/or/br330Dim br/bl/r1000No light  Is there a pattern in the amount of voltage drop across the resistors? The greater the resistance, the greater the voltage drop across the resistor.  Is there a pattern in the amount of voltage drop across the lamp? The greater the resistance, the less the voltage drop across the lamp.  How do these voltage-drop patterns relate to the size of the resistor in the circuit with the lamp? As resistance increases, the voltage across the resistor increases, and the voltage across the lamp decreases.  Add up the lamp and resistor voltages for each resistor. Is there a pattern? The sum of the voltage drops in the circuit equals the available voltage across the terminals of the battery.

 Hand in the “Resistor/Voltage Investigation” sheet.  Return the components to your bags  Secure the battery leads.  Turn the multi-meter off.  Return all materials to the materials station.