Basic physical concepts

What is Nonelectrical Energy?

In electricity and electronics there are many kinds of phenomena that occupy other forms of energy besides electrical energy. Visible light is an example. A light bulb converts electricity into radiant energy that you can see. This was one of the major motivations for people like Thomas Edison to work with electricity. Visible light can […]

What is Electromotive Force?

Current can only flow if it gets a “push.” This might be caused by a buildup of static electric charges, as in the case of a lightning stroke. When the charge builds up, with positive polarity (shortage of electrons) in one place and negative polarity (excess of electrons) in another place, a powerful electromotive force […]

Static electricity

Static Electricity | ElectroStatic Charge

Charge carriers particularly electrons can build up or become deficient on things without flowing anywhere. You’ve probably experienced this when walking on a carpeted floor during the winter or in a place where the humidity was very low. An excess or shortage of electrons is created on and in your body. You acquire a charge […]

Current Definition

Whenever there is movement of charge carriers in a substance there is an electric current. Current is measured in terms of the number of electrons or holes passing a single point in one second. Usually, a great many charge carriers go past any given point in one second, even if the current is small. In […]


Semiconductors Definition

In a semiconductor electrons flow but not as well as they do in a conductor. You might imagine the people in the line being lazy and not too eager to pass the balls along. Some semiconductors carry electrons almost as well as good electrical conductors like copper or aluminum; others are almost as bad as […]

Resistors Definition

Some substances such as carbon, conduct electricity fairly well but not really well. The conductivity can be changed by adding impurities like clay to a carbon paste, or by winding a thin wire into a coil. Electrical components made in this way are called resistors. They are important in electronic circuits because they allow for […]

Insulators Definition

If the people refuse to pass balls along the line in the previous example, the line represents an electrical insulator. Such substances prevent electrical currents from flowing, except possibly in very small amounts. Most gases are good electrical insulators. Glass, dry wood, paper, and plastics are other examples. Pure water is a good electrical insulator, […]



In some materials, electrons move easily from atom to atom. In others, the electrons move with difficulty. And in some materials, it is almost impossible to get them to move. An electrical conductor is a substance in which the electrons are mobile. The best conductor at room temperature is pure elemental silver. Copper and aluminum […]



When atoms of elements join together to form a compound, the resulting particles are molecules. Fig is an example of a molecule of water, consisting of three atoms put together. The natural form of an element is also known as its molecule. Oxygen tends to occur in pairs most of the time in the earth’s […]

Chemical Compound

Chemical Compound

Compounds Different elements can join together to share electrons. When this happens the result is a chemical compound. One of the most common compounds is water, the result of two hydrogen atoms joining with an atom of oxygen. There are literally thousands of different chemical compounds that occur in nature. A compound is different than […]


Electrons and Electricity

Surrounding the nucleus of an atom are particles having opposite electric charge from the protons. These are the electrons. Physicists arbitrarily call the electrons’ charge negative, and the protons’ charge positive. An electron has exactly the same charge quantity as a proton, but with opposite polarity. The charge on a single electron or proton is […]

Isotopes, Atomic Weights and Atomic Number

For a given element such as oxygen the number of neutrons can vary. But no matter what the number of neutrons, the element keeps its identity, based on the atomic number. Differing numbers of neutrons result in various isotopes for a given element. Each element has one particular isotope that is most often found in […]

Protons Neutrons and Atomic Number

The part of an atom that gives an element its identity is the nucleus. It is made up of two kinds of particles, the proton and the neutron. These are extremely dense. A teaspoonful of either of these particles, packed tightly together, would weigh tons. Protons and neutrons have just about the same mass but […]


All matter is made up of countless tiny particles whizzing around. These particles are extremely dense; matter is mostly empty space. Matter seems continuous because the particles are so small, and they move incredibly fast. Even people of ancient times suspected that matter is made of invisible particles. They deduced this from observing things like […]