image credit: ReignMan, Creative Commons; image source; larger image

Hyperphysics: Electric Guitars - Jun 1, 2012

This photo shows the electric guitar pickups from a Fender Stratocaster. Notice that there are three different pickup locations, and each location has a pickup (the circular dots) for every string. Each individual pickup contains a magnet, a coil, and thousands of turns of insulated wire wrapped around the magnet.

To find out how an electric guitar produces sound from a vibrating string, see Hyperphysics: Electric Guitars. To learn about the physics of vibrating strings, see this additional Hyperphysics page.

Image credit: Jupiter405; image source; larger image

Hyperphysics: Torque - May 1, 2012

Think about the forces on this sailboat: The force of the wind on the sail (perpendicular to the fabric of the sail), tends to rotate the boat. A force that can rotate an object is called a torque. In this case, if the torque of the wind isn't balanced, it will tip the boat over. The weight of the sailor, and also the weight of the hull that's out of the water, both create torques in the opposite sense, to balance the torque of the wind.

For more on torques, see Hyperphysics: Torque, and also this other Hyperphysics page.

image credit: CERN; image source; larger image

Hyperphysics: Electromagnetic Waves - Apr 1, 2012

In the photo above of a handheld citizens band radio, the metal coil is the antenna. When the radio is transmitting, the radio produces an electric current that surges back and forth in the antenna, which emits radio waves. And when the radio is receiving, radio waves induce a tiny alternating current in the antenna. The current in the antenna carries the radio signal.

For a drawing of an electromagnetic wave (radio waves are one example) see Hyperphysics: Electromagnetic Waves. To learn more about the CB antenna shown in the photo, go to this Wikipedia article and scroll down.

image credit: NASA; image source; larger image

Structure and Optical Isomerism - Mar 1, 2012

Have you noticed that the left hand is the mirror image of the right hand, but they cannot be superimposed? That's also true for some molecules containing carbon atoms. In the image above, the molecule on the left cannot be superimposed on the one on the right.

To learn more about such molecules, check out Structure and Optical Isomerism; also, click to see this movie.

Such left-handed and right-handed molecules rotate the plane of polarization of light in opposite directions. To find out more about polarized light and this important effect, click here. Also, you can learn how Louis Pasteur explained it.

image credit: NASA, Troy Cryder; image source; larger image

Kepler Mission - Feb 1, 2012

The NASA Kepler observatory searches for extrasolar planets by monitoring about 100,000 stars in a small patch of sky. The observatory looks for stars that periodically dim as a planet passes in front of the star. Kepler was launched in 2009, and by January, 2012, it had already found 33 confirmed extrasolar planets and about 2300 candidates. To learn more, visit Kepler Mission, then click on "About the Mission."

image credit: Carla Thomas, NASA; image source; larger image

How Things Work: Winglets - Jan 1, 2012

The photo shows two NASA F/A18s. The smoke streaming from the wingtip of the one on the right reveals the wingtip vortex, which increases the wing's drag. This vortex occurs because the pressure underneath the wing is greater than the pressure above the wing; this excess pressure generates a flow of air around the wingtip, creating the vortex. These vortices can trail behind the aircraft for miles, creating a hazard for following aircraft, particularly small ones.

To reduce the drag caused by these vortices, "winglets" have been added to the wingtips of some airliners, as you can see in this Wikimedia photo. To learn more, visit How Things Work: Winglets.

image credit: © Felice Frankel, from "Envisioning Science, the Design and Craft of the Science Image;" larger image

Ferrofluids - Dec 1, 2011

Physics becomes art in Felice Frankel's photo of a ferrofluid with permanent magnets underneath. In a ferrofluid, a region of approximately constant magnetic field produces a pattern of spikes.

A ferrofluid is a concentrated suspension of nanometer-sized magnetic particles. To learn more, see the Physics Central feature Ferrofluid Fun and also the videos at Ferrofluids.

image credit: Shaddack, Wikimedia Commons; image source; larger image

Relativity Powers Your Car Battery - Nov 1, 2011

If you own a car with a lead-acid battery, you might be interested to know that 80% of the voltage comes from Einstein's theory of special relativity. Lead works so well in storage batteries because its atom has a large nucleus, and the innermost electrons rotate at a significant fraction of the speed of light, bringing relativity into play. To learn more, visit Physical Review Focus' Relativity Powers Your Car Battery. For more on the special theory of relativity, visit this Stanford site.

image credit: U.S. Air Force; image source; larger image

What is a contrail and how does it form? - Oct 1, 2011

The contrails in the photo above were generated by an Air Force C-141 Starlifter. Jet fuel is a mixture of hydrocarbons, which burns to produce carbon dioxide and water vapor. The water vapor condenses upon cooling to form small water droplets--the contrail--which is essentially a cloud. To  learn more, check out What is a contrail and how does it form? from the National Weather Service. Like clouds, contrails can affect global warming--to  find out how, see From Physics Research and Worth a Look.

Image credit: HawaiianMama, Wikimedia Commons; image source; larger image

HyperPhysics: Global Positioning Satellites - Sep 1, 2011

The image shows a Global Positioning System (GPS) receiver that pinpoints a cyclist's location to an accuracy of about 10 m. The receiver analyzes radio signals from several GPS satellites, each containing an atomic clock accurate to about one second every 30,000 years. For more on GPS, see HyperPhysics: Global Positioning Satellites and also this NASA site.