SHPE Foundation Online SHPE Jr. Member Activities

TeachEngineering Hands-on

Activity: *

Light Your Way

TeachEngineering Digital Library: teachengineering.org

SHPE Foundation Online SHPE Jr. Member Activities

TeachEngineering Digital Library

http://www.teachengineering.org

• • • The TeachEngineering digital library provides over 1350 free engineering lessons and activities. Engineering lessons and activities connect real world experiences with curricular content already taught in K-12 classrooms.

TeachEngineering's comprehensive curricula are

hands-on, inexpensive, and relevant to students' daily lives.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way

Reference Activity on TeachEngineering • • •

Learn about circuitry through the design and construction of a portable flashlight!

Engineering focus:

o

Engineering Design Process

• Using limited materials, brainstorm, design, test and redesign until you have a functioning flashlight.

Learning objectives: o o o o Design and construct a working portable flashlight.

Define, recognize and assemble series circuits.

Explain the path of electrical charge through your circuit.

Describe the engineering process behind designing a flashlight.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way

• •

Suggested time:

60 minutes

Materials

o 2 D-cell batteries o o 5 pieces of insulated copper wire (various lengths; available at hardware stores) 1 #40 bulb (available at hardware stores) o o o o o 1 bulb holder (available at hardware stores) 1 cardboard paper towel or wrapping paper tube reflective material (aluminum foil, small pie tins, foil muffin cups, etc.) thumb tacks rubber bands o o o o masking tape wire strippers or medium-grade sandpaper (to remove insulation from wire ends) wire cutters scissors

Optional materials:

o thin flat strips of wood or plastic o switch (available at Radio Shack or other electronics stores) or a variety of materials to make a switch (paper clips, aluminum foil, nails, coins, insulated wire (possibly of varying gauges, keys, etc.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Engineering Connection

(Real World Application): • When

electrical engineers

design electrical equipment, they figure out the optimum

circuitry design

for the situation, whether it is the installation of solar panels, design of electric cars, behavior of traffic signals, hair dryer on/off switch, turn indicator lights on a vehicle or even a simple flashlight. They decide between creating a

parallel or series circuit

, or they often create a complex circuit system composed of both types.

Solar panels Flashlight Electric Car

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way

Vocabulary Terms

Alternating current (AC) Circuit diagram Direct current (DC) An electric current in one direction only.

Definitions

An electric current that reverses direction at regular intervals.

A graphical representation of a circuit, using standard symbols to represent each circuit component.

Energy transfer Load Parallel circuit The movement of energy within a system. Can include the transformation of one type of energy to another (with some loss). Relevant examples include electricity to motion (fan), electricity to light and heat (light bulb), electricity to sound and motion (sound system).

A device or the resistance of a device to which electricity is delivered.

An electric circuit providing more than one conducting path.

Resistor Series circuit A device used to control current in an electric circuit by providing resistance.

An electric circuit providing a single conducting path such that current passes through each element in turn without branching.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way

• •

Introduction:

Consider why some electronic games or toys require more batteries than other games or toys. (Some toys need more power, some games need more electricity.) Three AA batteries connected

“in series”

batteries can be "in series" or can provide more voltage than a single AA battery. Electrical circuits as well as

”in parallel”

.

How do electrical engineers know how many batteries are needed to operate an electronic game or toy? They create a map of the circuit, or

circuit diagram

the power the device needs to operate.

, to determine the necessary voltage and current to supply

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way

• •

Introduction:

Why do some devices use batteries and other devices use a wall outlet for power? (Batteries produce a different type of current than a wall outlet.) The current that comes from a battery is called called

direct current (DC) alternating current (AC)

. . The current that comes from a wall outlet in our homes or schools is Many televisions, computers, DVD players and stereos have hardware (equipment) inside the device that converts the alternating current (AC) to direct current (DC) for operation of the device.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Circuit Diagrams:

o o o o

Circuit Diagrams

language of are graphical representations of circuits or electrical devices; the circuit diagram is the

electrical design and engineering

.

Each component of a circuit has a corresponding standard symbol. In circuit diagrams, symbols are linked together to show the circuit construction – the diagram is a map that anyone can read to learn how to build the circuit.

Interpreting circuit diagrams is an essential skill for

electrical engineers

and many other types of engineers.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way How are Electrical Elements Connected in a Circuit:

o o o

In series

- When the parts of a circuit are connected such that there is a single conducting path between them.

In parallel

circuit.

– When circuit elements are connected across common points such that there is more than one conducting path through the A typical electrical device is composed of many smaller series and parallel portions.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Ohm’s Law and Series Circuits:

o Ohm’s Law is a fundamental mathematical equation describing the relationship between voltage, current and resistance. o

R = V/I

, where R = resistance of a circuit element, V = total voltage supplied to the circuit by a power source (battery), and I = current through the circuit.

o

V = I*R

– Ohm’s Law for predicting a voltage drop across a circuit element with a known resistance and a known current passing through. o The voltage supplied to the circuit, V, and the total voltage drop throughout the circuit is equal to I*R T = V T , where R T is the total resistance in the circuit.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Ohm’s Law and Series Circuits:

o o o o o In the diagram below, there is only one path for charge movement through the circuit, the current is the same throughout the circuit As electrons move through the circuit, their flow is resisted by each light bulb, such that the total resistance to charge movement is the sum of all the resistances in the path.

I = V/R

– total current is equal to the voltage divided by the total resistance.

There is a voltage drop across each bulb. The sum of the voltage drops is equal to the voltage of the power source (battery) The voltage drop across each light bulb is directly proportional to that bulb’s resistance (

V = I*R

)

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Ohm’s Law and Series Circuits:

o When batteries are linked in series, the total voltage is the sum of the voltages of each battery.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way DC v. AC:

o o

Direct current (DC)

is the movement of charge in a circuit in one direction only. Batteries, photovoltaic cells and some generators provide direct current (DC). • In a battery-powered flashlight, electrons leave the negative terminal of the battery and move through the flashlight circuit to the positive terminal. In

alternating current (AC)

position in the circuit. , electrons move back and forth in a circuit. The electrons only move a small distance around a relatively fixed • • • AC has been proven to be a more effective way to transmit electrical power. Whenever you plug an electrical device into a wall socket, you are using AC. The current direction alternates because the direction of voltage is alternated at the power plant. In the US, we use current that changes direction 60 times a second.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Background on the Flashlight:

o o o The first flashlight was invented in 1896, made possible by the invention of the D-cell battery.

Called “flash lights” because they provided a brief flash of light when the user pushed a switch – unlike the steady light beam produced by today’s flashlights. Over time, the parts of a flashlight haven’t changed much! The flashlight you will build in this activity has all these parts except for the protective glass and the spring.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Procedure Overview

o o Consider the components that make up a typical flashlight, then design, build, and test your own flashlight.

Note: if you are using pre-made switches, you will not need to assemble any switch materials.

The basic circuit for a flashlight

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Procedure

1. Open-ended design: The goal of this activity is to design and construct a working flashlight using only the listed materials. The flashlight must turn on and off using a switch. Also, all of the wiring and batteries must be contained within the paper towel tubes.

2. Consider the qualities of a good flashlight. (On/off switch, reliable switch, easy-to-use switch, easy to carry, small size, bright beam of light, lasts a long time, does not break) 3. Draw a flashlight. (Parts include: case, spring, bulb, switch, protective glass/plastic, reflector, batteries) Consider the function of each part of the flashlight that has been drawn.

4. Brainstorm the design of your flashlight, determining which materials you will use for each part. Document your material plans.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Procedure

5. Draw a circuit diagram for your flashlight. Write out the steps you are going to take to build your flashlight.

6. With the listed materials, construct your flashlight design.

7. Test your flashlight. To be considered reliable, it should be able to light up three times in a row. If your flashlight does not work, compare the flashlight circuit diagram to your flashlight’s circuit.

8. Write down any design changes or fabrication improvements you need to make, and implement the changes so the flashlight works.

The circuit diagram

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Safety Issues

o o Do not play with the insulated wire Do not hold the insulated wires on the D-cell battery with you fingers for extended periods of time. The stripped ends of the wire heat up when held on the battery terminals.

Troubleshooting Tips

o o o o Slice small cardboard tubes down the middle to accommodate the D-cell batteries.

A paperclip may be used to hold the light bulb in place.

Make sure all of your connections are reliable, so when you move the flashlight, the connection doesn’t come loose.

Ideally, all of the wires used in the flashlight should be contained within the paper towel tube – no wires should be hanging out. If you have problems making the switch inside the tube, set up your switch externally.

SHPE Foundation Online SHPE Jr. Member Activities

Light Your Way Sales Pitch!

o Pretend to be a salesperson who are trying to sell your flashlights to a manufacturer or a consumer. Create a persuasive power or flyer, as well as a 10-minute sales pitch of your flashlight design for presenting to a friend or family member. Incorporate into your sales pitch your series circuit diagram, the parts and the feel of the flashlight and how it works.

Activity Extension

o Portable flashlights can be powered by means other than batteries. Conduct Internet research on solar-powered flashlights, "shake" flashlights and "crank" flashlights. Consider the environmental and economic implications of using these types of flashlights.

SHPE Foundation SHPE Jr. Chapter Curriculum Hands-On Activity Training • •

TeachEngineering

Contact Information

TeachEngineering:

http://www.teachengineering.org/ o over 1,350 standards-based engineering lessons and activities Carleigh Samson, TeachEngineering Editor o o [email protected]

303.492.6950

Questions?

http://www.fws.gov/refuge/Stone_Lakes/FAQ.html/