Variable Resistors and Potentiometers

Resistor Construction | Variable Resistors and Potentiometers

The materials used for resistor construction are generally metal alloys, pure metal or metal-oxide films, or carbon (solid or in thin-film form). Wire wound resistors use metal alloy wire wound onto ceramic formers. The windings must have a low self-inductance value, so that the wire is wound using the method shown in Figure 1 with […]

Values Of Resistivity And Conductivity At 00

How to do Resistivity Calculations?

Because the resistivities of commonly used materials are well known and can be looked up in tables, to find the resistance in ohms of a piece of wire of known length and diameter the formula is more useful in the form: R = pL/A with p in ohm-metres, L in metres and A in square […]


What is Resistivity?

The resistance of any sample of a material is determined by its dimensions and by the value of resistivity of the material. Wire drawn from a single reel (with uniform diameter) will have a resistance that depends on its length. For example, a 3 m length will have three times the resistance of a 1 […]

Resistors and Non-ohmic Behavior

Resistors and Non-ohmic Behavior

The resistance of a sample of material, measured in units of ohms (W), is defined as the ratio of voltage (in units of volts) across the sample of material to the current (in units of amperes) through the material. The name ampere is usually abbreviated to amp. When we draw a graph of voltage across […]

Passive Components and Active Components

Passive Components and Active Components

Passive Components Passive components are those that need no power supply for their operation and whose action will dissipate power, though in some cases the amount of dissipation is negligible. No purely passive component can have an output that supplies more power than is available at the input. Active Components Active components, by contrast make […]

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 […]

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