|
A single “D” battery can supply an astonishing 75,000 J of energy! If you could get all the energy out in one second that would be the equivalent of 100 horses, from a package that fits in the palm of your hand. Fortunately, 1.5 volt batteries can’t deliver electrical power so quickly, or they would be very unsafe. 
| 
|
|
Electricity exists because matter has a property called electric charge, which is normally hidden. Inside atoms are negatively charged particles called electrons and positively charged particles called protons. Under special circumstances, such as dragging your feet across a carpet on a dry winter day, you can sense electric charge in the form of a spark from static electricity. Lightning is another way to see the effects of electric charge—but hopefully not to experience it!
|
|
Magnets seem to have little to do with electricity but magnetism and electricity are two faces of the same fundamental phenomenon. In the late 19th century physicists discovered that electric current can cause magnetism. Electromagnetism is the operating principle behind electric motors, generators, computer disk drives, and countless other technologies.
|
Light is an electromagnetic wave and it interacts with individual atoms. What is an atom? Consider cutting a piece of aluminum foil into the smallest possible bits, then using a microscope to divide those bits into smaller bits, and the smaller bits into even smaller bits, and so on. At some point you come to a single atom of aluminum, which, at 0.00000001 m in diameter, is the very smallest particle of aluminum there can be. If you divide the atom further by separating some protons, neutrons, or electrons, you will no longer have aluminum at all but some other element.
|
|
When technology was developed that allowed us to actually observe how electrons and protons behaved inside atoms, and how light interacted with single atoms, we found something completely new. Quantum physics was invented to explain the universe on very small scales. It is both a crowning intellectual achievement for its accuracy at describing the world of atoms and also a profound mystery because it causes us to completely rethink almost everything we know about how the world works. An electron with a mass of 9.1 × 10−31 kg does not behave at all like a tiny marble that is simply a million trillion trillions times smaller than usual.
|
|
Many technologies in use—such as the MRI scanner in a hospital or a computer—explicitly depend on quantum physics. The laser in a laser cutting machine is based on stimulated emission, which is a quantum phenomenon. The quantum world is extraordinarily rich and surprisingly not well explored. A superconducting wire that carries electricity without friction is one potential quantum technology that may become reality in the decades to come.
|
Electricity and magnetism are two unique phenomena that interact and affect each other. They are often referred to collectively as electromagnetism. Many technologies use the principles of electricity, magnetism, or both to transfer energy and accomplish work. Indicate whether the following technologies use electricity, magnetism, or both. - compass
- battery-powered motor
- flashlight
 |
- A compass utilizes magnetism. A magnetized needle aligns itself with the Earth's magnetic field and points toward the north pole.
More advanced versions of compasses, such as the magnetometer or global positioning system (GPS), use electronics to make accurate measurements of magnetic fields and provide more accurate information about the location and conditions. - A battery-powered motor utilizes electricity and magnetism. The battery provides electrical energy that flows to the motor. The motor converts the electrical energy to mechanical energy with magnetic fields that cause a magnet to move. The movement of the magnet is the movement of the motor.
A simple electric motor can be found in everyday objects such as a rotating fan, a blender, and a battery-powered analog clock. - A flashlight utilizes electricity. A conventional flashlight contains a simple electric circuit with a battery, a light bulb, and a switch.
Some kinds of flashlights are mechanically powered; these use a hand crank to produce electrical energy from mechanical energy. This is an example of a generator, which is the opposite of a motor. These kinds of flashlights use magnets to convert the energy, because moving magnets induce electrical charge in wires. 
|
| |
|
