How does resistance work

But today, degrees Centigrade is more common and acceptable. Special wire alloys are formulated to have special temperature coefficients.

These, and other alloys allow us to "tailor" the resistor to desired characteristics in applications where temperatures change. In the same application, a resistor made with Evenohm wire would increase to only ohms. There is another quantity that is similar to resistance. It is called "reactance. Reactance only occurs in electrical or electronic circuits if the current flow is changing rapidly.

It is usually important in "alternating current" AC circuits where the current periodically changes direction and amplitude at some rate called "frequency. Reactance occurs because all circuit elements have "inductance" and "capacitance. However, the inductance of wire wound resistors can be critical! All conductors have some inductance. When the conductor is coiled, as it usually is in wire wound resistors, this inductance becomes larger. In AC circuits, inductance causes "inductive reactance.

Inductive reactance increases as the frequency of the alternating current increases. For example, a resistor might have enough inductance to create one ohm of reactance at a frequency of 60 Hz cycles per second. If we increase the frequency to 6, Hz an audio frequency , the reactance would increase to ohms.

Increasing the frequency to 6,, Hz a radio frequency , increases the resistor's reactance is 10, ohms. Obviously, the inductance of wirewound resistors can be significant in AC circuits! When reactance is important in AC circuit applications, Riedon can wind the wire in a special way to eliminate or reduce the resistor's inductance.

Download Our Brochure. Our production facilities will be shut down Friday, December 24th, returning Monday, January 3rd, The equation representing the dependency of the resistance R of a cylindrically shaped conductor e.

Consistent with the discussion above, this equation shows that the resistance of a wire is directly proportional to the length of the wire and inversely proportional to the cross-sectional area of the wire.

As shown by the equation, knowing the length, cross-sectional area and the material that a wire is made of and thus, its resistivity allows one to determine the resistance of the wire. Resistors are one of the more common components in electrical circuits. Most resistors have stripes or bands of colors painted on them.

The colors reveal information about the resistance value. Perhaps you're doing a lab and need to know the resistance of a resistor used in the lab. Use the widget below to determine the resistance value from the colored stripes. Household circuits are often wired with two different widths of wires: gauge and gauge. Thus, gauge wire has a wider cross section than gauge wire.

A Amp circuit used for wall receptacles should be wired using gauge wire and a Amp circuit used for lighting and fan circuits should be wired using gauge wire. Explain the physics behind such an electrical code. A gauge wire is wider than gauge wire and thus has less resistance. The lesser resistance of gauge wire means that it can allow charge to flow through it at a greater rate - that is, allow a larger current.

Thus, gauge wire is used in circuits which are protected by Amp fuses and circuit breakers. On the other hand, the thinner gauge wire can support less current owing to its larger resistance; it is used in circuits which are protected by Amp fuses and circuit breakers.

Based on the information stated in the above question, explain the risk involved in using gauge wire in a circuit that will be used to power an ampere power saw. Resistor markings come in three types, 4, 5 or 6 banded. With 4 banded resistors the first two bands tell you digits the third band tells you the multiplier and the fourth band tells you the tolerance which is how variable the actual resistance value from the stated one will be.

With 5 banded resistors the first three bands tells you digits, the fourth band tells you multipliers and the fifth band tells you tolerances. Skip to content. What is resistance? Let us start with conductors and insulators. Basically conductors allow electricity to flow and insulators stop electricity. For example air is normally an insulator, but with a large enough voltage it becomes a conductor as we see when lightning forms in an electrical storm.

A conductor can be better explained as having a low resistance and an insulator as having a high resistance. I is Current measured in amps written as A. In fact there is a relationship between voltage, resistance and current.

Knowing two of the variables, it is possible to calculate the third. The relationship between resistance, voltage and current is known as Ohm's law and it is one of the fundamental relationships in electrical and electronic science. The basic unit of electrical resistance is the Ohm as already mentioned.

In addition to this the basic unit can be prefixed by multipliers. This is because the range of values for electrical resistance can span many decades and it is necessary to have an easy notation that does not rely on counting the numbers of zeros in a number as this would easily lead to mistakes. Occasionally resistances less than an ohm are encountered, these are measured in milliohms m thousandths of an ohm.

The reason for this is that the Greek letter omega is not as easy to use as the prefixes R, k, and M. In order that the current can be limited in a particular circuit, a component known as a resistor may be used. Resistors come in a variety of forms from large wired components, or even some using terminals to the very small surface mount components used in many electronics circuits today.

Resistors can be made from a variety of materials, carbon, metal oxide, metal film, resistance wire and the like. Resistors can come in different formats - different types of resistor have slightly different characteristics and this means that they may be used in different circuit applications.

Selecting the right type of resistor can help the circuit operate in the way it is intended.