Maybe somewhere in your home there's a long hallway or a stairway with a light that you can turn on from either end. It's a nice convenience, but did you ever wonder how it's wired up to work that way? The goal of this project is to build a similar circuit with switches, flashlight batteries and a flashlight bulb (obviously, household circuits are not safe to experiment with). You'll need to understand the difference between connections made in series and connections made in parallel in an…
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An electric current produces a magnetic field. You can take advantage of this fact to make a simple apparatus to test the electrical conductivity of various materials, including both solids and liquids. The detector consists of a coil of wire, with a magnetic compass inside it. You connect one end of the coil to a D-cell battery. The other end of the coil is connected to whatever material you are testing, and the material, in turn, is connected to the other end of the D-cell. In other…
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You may know Lewis Carroll as the author of Alice in Wonderland, but did you know that in real life he was a mathematician who studied symbolic logic and logical reasoning? How can math help you solve Lewis Carroll's Logic Game? (Bogomolny, 2006) How are algorithms for solving the game Sudoku similar to solving a logic problem? (Hayes, 2006) For the super-advanced mathematical genius, try to evaluate currently available, logic-based computational tools, or design a better one!…
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In the United States, lighting for homes accounts for about 14% of all residential electricity usage (EIA, 2014). That's billions of dollars worth of electricity per year. The U.S. has passed legislation to phase out older, more inefficient incandescent light bulbs, and they are being replaced with newer, more-efficient bulb types like compact fluorescent lights (CFLs) or light-emitting diodes (LEDs). How much energy (measured in kilowatt-hours [kWh]) and how much money could be saved by…
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A magic square is an arrangement of numbers from 1 to n2 in an n x n matrix. In a magic square each number occurs exactly once such that the sum of the entries of any row, column, or main diagonal is the same. You can make several magic squares and investigate the different properties of the square. Can you make an algorithm for constructing a Magic Square? Can you show that the sum of the entries of any row, column, or main diagonal must be n(n2+1)/2? Are there any other hidden properties of a…
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What do you do with your old wooden pencils when they get too short to hold? Don't throw them away; you can use them to make circuits! This project will show you how to use pencils to make resistors, an important part of many electrical circuits, and test how they affect the brightness of a lightbulb in a simple circuit.
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Elec_p013

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Time Required

Average (6-10 days)

Prerequisites

None

Material Availability

A kit for this project is available from the . Estimated project time includes time for shipping the kit.

Cost

Low ($20 - $50)

Safety

Short circuits can get very hot and present a burn hazard. Never connect the positive and negative ends (red and black wires) of the battery pack directly to each other. Adult supervision is required for cutting the pencils.

LEDs (light-emitting diodes) are electronic components that convert a portion of the electrical energy flowing through them into light. How does the intensity of the light produced vary with the current flowing through the LED? To find out, you'll build some simple circuits to vary the current flowing an LED. You'll also build a simple light-to-voltage converter circuit to measure LED output.
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Water is a valuable resource, and water shortages are a serious problem in many parts of the world. The problem can be made worse by people who waste water; for example, by watering a garden or using sprinklers on their lawn (or a farmer taking care of an entire field) when it has rained recently or the soil is already moist. How can you help conserve water and prevent such waste? One way is to build an electronic soil moisture sensor. This project will show you how to build a circuit that…
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Elec_p066

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Time Required

Average (6-10 days)

Prerequisites

Familiarity with using a solderless breadboard, or willingness to learn.

Material Availability

Specialty electronics items are required. A kit is available from the . Time required includes shipping for the kit.

Cost

Average ($50 - $100)

Safety

Short circuits can get very hot. Double-check all of your wiring before you connect the 9 V battery.

Solar cells are an alternative method for generating electricity directly from sunlight. With this project, you can get down to the atomic level and learn about the world of solid-state electronics as you investigate how solar cells work. Your experiment will measure the effect of changing light intensity on power output from the solar cell. A possible variation would be to investigate the effect of changing the color of the light.
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Energy_p014

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Time Required

Short (2-5 days)

Prerequisites

None

Material Availability

Specialty electronics components required, see Materials list for details

This a straightforward, but interesting, project in geometry. It is a good first proof to try on your own. You should be able to figure it out by yourself, and you'll gain insight into a basic property of circles.
Figure 1 below shows a semicircle (AE, in red) with a series of smaller semicircles (AB, BC, CD, DE, in blue) constructed inside it. As you can see, the sum of the diameters of the four smaller semicircles is equal to the diameter of the large semicircle. The area of the larger…
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Math_p010

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Time Required

Very Short (≤ 1 day)

Prerequisites

Must understand the concept of a mathematical proof