Electric Resistance – The Physics Hypertextbook
Today you'll learn the relationship between resistance and temperature. relationship%2Bbetween%2Bresistance%2Band%2Btemperature. Originally Answered: What is relation between resistance and temperature? Materials vary: most metals show increasing resistance with temperature - an effect. Or, expressed in terms of the resistance at some standard temperature from a to the mean free path between collisions (d), and for temperatures above about.
The following table gives the temperature coefficients of resistance for several common metals, both pure and alloy: Setting up a table of voltage, current, and resistance values we get: At 20o Celsius, we get If the temperature were to rise to 35o Celsius, we could easily determine the change of resistance for each piece of wire. Recalculating our circuit values, we see what changes this increase in temperature will bring: As you can see, voltage across the load went down from Though the changes may seem small, they can be significant for power lines stretching miles between power plants and substations, substations and loads.
In fact, power utility companies often have to take line resistance changes resulting from seasonal temperature variations into account when calculating allowable system loading. Materials are important as well.
A pipe filled with hair restricts the flow of water more than a clean pipe of the same shape and size.
Temperature Coefficient of Resistance
Similarly, electrons can flow freely and easily through a copper wire, but cannot flow as easily through a steel wire of the same shape and size, and they essentially cannot flow at all through an insulator like rubberregardless of its shape.
The difference between copper, steel, and rubber is related to their microscopic structure and electron configurationand is quantified by a property called resistivity. In addition to geometry and material, there are various other factors that influence resistance and conductance, such as temperature; see below. Conductors and resistors[ edit ] A 6. An ohmmeter could be used to verify this value.
Relationship between Resistance and Temperature
Substances in which electricity can flow are called conductors. A piece of conducting material of a particular resistance meant for use in a circuit is called a resistor. Conductors are made of high- conductivity materials such as metals, in particular copper and aluminium.
Resistors, on the other hand, are made of a wide variety of materials depending on factors such as the desired resistance, amount of energy that it needs to dissipate, precision, and costs.
Ohm's law The current-voltage characteristics of four devices: Two resistorsa diodeand a battery. The horizontal axis is voltage dropthe vertical axis is current. Ohm's law is satisfied when the graph is a straight line through the origin.
Therefore, the two resistors are ohmic, but the diode and battery are not. The more the atoms jostle around in the material, the more collisions are caused and hence the greater the resistance to current flow.
Electrical resistance and conductance - Wikipedia
In an insulator however, there is a slightly different situation. There are so few free electrons that hardly any current can flow.Resistance of a metal wire as temperature increases
Almost all the electrons are tightly bound within their particular atom. Heating an insulating material vibrates the atoms, and if heated sufficiently, the atoms vibrate violently enough to actually shake some of their captive electrons free, creating free electrons to become carriers of current.
Therefore at high temperatures the resistance of an insulator can fall, and in some insulating materials, quite dramatically. Different materials within either group have different temperature coefficients. Materials chosen for the construction of the resistors used in electronic circuits are carefully selected conductors that have a very low positive temperatur coefficient.
- Electric Resistance
- Electrical resistance and conductance