125 Physics Projects for the Evil Genius (3 page)

Some labs also have adjustable power supplies built into the lab benches. If your DC power supply consists of a battery, the voltage can be made variable by using various combinations of resistors. Other options for a power supply include a hand-held generator that produces a DC voltage when a crank is manually turned (such as PASCO, part number EM-8090 or SE-8645, or Sargent-Welch, part number WL2420).

Figure I-1
Power supply. Courtesy PASCO
.

• batteries—
  C
  or
  D
  cell battery and holder. You will not need a battery if you have a DC power supply except for
  Project 113
  .
  
• electrical meters—the most useful and versatile meter is a multimeter. Multimeters perform the functions of ammeters, voltmeters, ohmmeters, and many can also be used as a digital thermometer. Multimeters can be acquired for less than $50, which in many cases is less expensive than stand-alone ammeters or voltmeters. Some projects require
  both
  an ammeter and a voltmeter, so for those projects,
  two
  multimeters are needed. If a multimeter is not available, a separate ammeter and voltmeter are needed.
  Figure I-2
  shows a multimeter available from Sargent-Welch, part number WLS-30712-60 (also from PASCO, part number SE 9786A, or Frey, part number 15-531978-21) that works with all the projects in this book. One word of caution: the multimeter is much more versatile than a dedicated ammeter or voltmeter for most purposes. However, if used incorrectly, such as by being placed in series with too high a current, you can either blow a fuse, or worse, damage the meter.
  

Figure I-2
Multimeter. Courtesy PASCO
.

• galvanometer—a galvanometer is a very sensitive ammeter that displays small electrical currents.
  
• electroscope—this is a simple device that measures the presence of static electric charges. They are inexpensive and available commercially. Homemade versions consist of a small ball attached by a wire. The wire is connected to two metal foil leaves, which are protected from discharge and air currents by a glass enclosure.
  
• magnets—bar and horseshoe magnets
  
• glassware—beakers, flasks
  
• rubber stoppers—two-hole and no-hole rubber stoppers to fit flasks
  
• hotplate—preferably adjustable with a ceramic top
  
• alcohol thermometer—mercury thermometers are no-no’s in most labs today because of the environmental problems created if they break.
  
• hydrogen tube with high-voltage power supply
  
• calculator—very often the ideas and key insights in physics are revealed and discovered by doing a calculation. A simple scientific calculator, such as a TI-30 or equivalent, can be helpful in many of the projects in this book.
  
• Computers are used in many ways, including:
  

– Collecting data from motion sensors and other measurement devices (such as light, sound, force, current, and voltage sensor).

– Analyzing data in a spreadsheet, such as Excel, to identify mathematical models.

– Sound card oscilloscope (see
Project 64
).

• laser pointer—a laser pointer with a replaceable (or, better yet, rechargeable) AA battery is the most versatile in the long run. The simple laser pointer available in many dollar stores works well, but is less reliable.
  
• lenses—convex, concave, semicircular, rectangular, 45-degree, 60-degree, and right-angle prisms. Some lenses are “smoky,” consisting of scattering particulates in the glass that make the light beams visible in the lens. Other lenses have a magnetic backing that makes them convenient to mount on a magnetic chalkboard or whiteboard. This makes it easy to enable ray tracing on a chalkboard. It is possible to glue a strong magnet to a lens, so they can be mounted on a chalkboard.
  
• mirrors—flat, concave, convex
  
• tape—duct tape, masking tape, electrical tape. One often-overlooked principle of physics is there is no such thing as having too much tape.
  

• motion sensor—for less than the cost of a video game console, you can get a motion sensor that connects with your computor. Motion sensors (such as PASCO, part number PS-2103A) enable measurement of an object’s position for various times.
  Figure I-3
  shows the motion sensor. The Data Studio software that comes (free) with PASCO motion sensors lets you generate graphs of distance versus time, velocity versus time, and acceleration versus time with little prior experience with this equipment. The motion sensor requires a simple interface to the computer. The simplest of these approaches connects to the computer’s USB port (PS-2100A) and requires no additional electrical power. Three sensors can be connected to a computer using the PS-2001.
  

Figure I-3
Motion sensor. Courtesy PASCO
.

• A hand-held data logger such as PASCO’s Xplorer GLX (part number PS-2002) functions in a similar way with various sensors eliminating the need for a computer. This also enables measurements to be taken at more remote locations.
  
• oscilloscope—wave forms generated by sound picked up by a microphone or electrical signals can be displayed graphically on an oscilloscope. If you have one, you can do a number of interesting things with a scope. Because each oscilloscope is somewhat different, you also need a good manual or a patient friend to get you started. If you do not have a physical oscilloscope, you can inexpensively acquire software that can enable the sound card commonly available in computers to serve as a surprisingly functional oscilloscope. Details on how to do this can be found in
  Project 64
  .
  
• dry ice—the cloud chamber described in
  Project 125
  uses dry ice, which can be obtained from welding supply companies, scientific labs, or chemical specialty companies. If you are able to get dry ice, you may want to get a little extra to explore other low-temperature physics experiments. Because dry ice, which is actually solidified carbon dioxide, is so cold, you should take precautions to avoid prolonged contact with the body. Use eye protection when working with dry ice, especially if you are breaking it into smaller pieces.
  
• Hover Puck—some physics labs use air tracks to eliminate friction. A lower-cost option is to use a Hover Puck that floats in a nearly frictionless manner across the floor. This is called out as an option in a few of the experiments in this book. Hover Pucks are available from PASCO, part number SE-73358, and Kick It Stick It Disc from Sargent-Welch, part number WLS-1764-09.
  
• liquid nitrogen—liquid nitrogen is needed to make the ceramic material described in
  Project 106
  cold enough to become superconducting. As with dry ice, liquid nitrogen is a material that is interesting in it own right and is explored in
  Project 92
  . It may make sense to plan both activities together. Just so you know: dry ice does
  not
  get cold enough to do
  Project 106
  and liquid nitrogen is not recommended for
  Project 125
  because it is too cold. Liquid nitrogen must be stored in a specially designed thermal container called a
  liquid nitrogen dewar
  , which safely handles the pressure that builds as the liquid nitrogen warms up. A regular thermos bottle with a sealed cap or any other type of sealed container should not be used. Liquid nitrogen is distributed in specially designed storage cylinders to organizations that do low-temperature studies, thermal cycling to test product reliability, and that use large volumes of gaseous nitrogen.
  
• vacuum pump—a vacuum pump is used in
  Projects 18
  ,
  41
  , and
  94
  .
  

Not so many years ago, some of the greatest physics experiments remained the province of obscure physics labs in exclusive universities. Today, these experiments are within the reach of many physics departments with a moderate budget. Because the price tag for doing these experiments is thousands, rather than hundreds, of dollars, for most of us, they are considered here to be wish-list experiments. For each of these, a simpler, low-budget option is presented. The three wish-list experiments referred to in this book are:

• Millikan oil-drop experiment (PASCO, part number AP-8210, and Flinn Scientific, part number AP5671)
  
• photoelectric effect apparatus, such as the Daedelon EP-05 (available from
  www.daedelon.com
  or Flinn Scientific, part number AP5768).
  
• Cavendish gravitational constant (PASCO, part number AP-8215)
  

At the other end of the funding spectrum are items that can be adapted for use in physics experiments. As has been demonstrated by many of the great scientists of the past, much can be accomplished through resourcefulness and ingenuity. Besides the bargain hunters and antique dealers, physics enthusiasts can, on occasion, be observed looking for unnoticed treasure at yard sales where other people fail to see the true value. Here are some of the items you might want to add to your bag of tricks.

• bowling ball—a bowling ball makes a good pendulum mass that can also give one of the most accurate measurements of gravitational acceleration. A bowling ball can be used in
  Projects 19
  ,
  22
  ,
  26
  , or
  66
  , if available. A heavy-duty screw eye can be anchored by taping into a pilot hole smaller than the diameter of the screw. Be careful and thoroughly test your mechanical connection before experimenting. Bowling balls can also come in handy in investigating collisions.
  
• swivel chair—you want one that rotates with as little friction as possible. This is useful in the conservation of angular momentum studies. Just the bottom part without the seat can be used for studying spinning objects.
  
• bathroom scale—this can be used to explore static equilibrium and torque.
  
• blow dryers—a blow dryer is a handy way to produce a reasonably steady air flow. This is used to explore Bernoulli’s principle in
  Project 43
  .
  
• fish tanks—the ones with glass bottoms are especially useful for optical projects using laser beams. A fish tank can be made into a cloud chamber in
  Project 125
  or used as the container of a mousetrap-fission demonstration in
  Project 123
  .
  
• slide projectors—old slide projectors or moving projects can be good sources of light.
  
• laser levels—these can be used like a laser pointer. The beams are angled to produce a visible line along a wall, which can be advantageous for ray tracing. The output may not be the best-focused point source of light, so this is not the best choice, for instance, to use with a diffraction grating.
  
• turntables—turntables can be adapted for rotation experiments. (This can also be useful for the digital generation to see what a historic device like the phonograph looked like.)
  
• air hockey games—these work well with CDs as pucks and can be a good way to investigate elastic collisions.
  
• skateboards, rollerblades—to demonstrate Newton’s third law.
  
• leaf blower—if you have a leaf blower, you have most of what you need to put together a one-person hovercraft. With just the right-shaped opening these can be used to levitate a beach ball in a demonstration of Bernoulli’s principle (
  Project 43
  ).
  
• bicycle tires—these make good gyroscopes and can be used for angular momentum experiments such as in
  Project 57
  .
  
• Christmas tree lights—these are an inexpensive and easy way to study electrical circuits such as in
  Project 100
  . They usually come in strands of series and parallel combinations.