Variation of Resistance

Voltage sources include devices such as batteries, cells, and other components that are required to maintain a potential difference across the circuit. When a voltage source is linked across a conductor, an electric field is created, causing charges to shift and current to flow. The current values that are generated are determined by the material’s properties.

The flow of electric charge is opposed by any material, which is known as resistance. It develops as a result of the material’s resistivity, which is a property. Let’s look at how these attributes change when the temperature changes.

Resistance

If the current is considered to be water and the pipe is considered to be the conductor through which the current is flowing, the water moving through the pipe will experience resistance. In the case of current, the same analogy can be used to determine the blockage of flow. Resistance is the hindrance of flow against the current. The resistance in a wire with current I and voltage V is defined as follows:

R=V/I

Here, R represents the resistance of the wire and its SI unit is ohms.

The resistance of a wire is proportional to the current flowing through it. As a result, the more resistance a wire has, the less current it can carry, as may be determined from the conventional definition of resistance.

Resistance of a Wire

Using the prior example of flowing water, one can see how these two very dissimilar physical processes are comparable. The amount of resistance provided to water flowing through the pipe is mostly determined by the pipe’s length and cross-sections. Similarly, the resistance provided by a conductor is determined by its size, shape, and substance. 

The conductor’s resistance is given by

R=ρl/A

Resistivity

When a voltage is supplied to a conductor, it creates an electric field E inside it, which causes the charges to move. The amount of current that develops is determined by the material and the electric field that is formed. This density can be somewhat complicated, but it can be calculated using reasonable assumptions, such as the metals being at room temperature. The following equation can be used to model this relationship:

J=σE

The SI unit of Resistivity is ohm-meter

Temperature Dependence of Resistance

The resistance of a material is determined by its resistivity, shape, and size, as stated in the formula above. A material’s resistance is determined by how its form varies with temperature and how its resistivity changes with temperature. Different materials’ resistivity changes with temperature in different ways. Conductors usually have a low resistivity, whereas insulators have a high resistivity. For different materials, resistivity fluctuates in a different way. In general, when it comes to metallic conductors:

The following equation describes the resistivity of metallic conductors over a limited temperature range:

ρT=ρ0[1+a(T-T0)]

Here,

ρT= Resistivity at temperature T

ρ0= Resistivity at temperatureT0.

a is the temperature coefficient of resistivity.

Various materials have different resistivity. Materials such as manganin and nichrome, for example, are less likely to vary their resistivity with temperature. The resistance of semiconductors reduces as the temperature rises.

Alloys resistivity grows with temperature as well, but at a considerably slower rate than metals, despite the fact that non-metals resistivity reduces as temperature rises. 

Semiconductors exhibit similar behavior; the temperature coefficient of resistivity is negative for semiconductors and nonmetals, and its value is frequently large for semiconductor materials.

Conductivity

The ease with which electric current can flow through a material is measured by its conductivity. Specific conductance is another name for it. A substance’s conductivity is the inverse of its resistance. The higher the resistivity value, the lower the conductivity value, and vice versa.

It is represented by the symbol σ.

σ=1/ρ

Where ρ is the resistivity.

Conclusion

In this article we have studied resistance, resistivity and also describe how it changes. With respect to the Temperature. If the current is considered to be water and the pipe is considered to be the conductor through which the current is flowing, the water moving through the pipe will experience resistance. In the case of current, the same analogy can be used to determine the blockage of flow. Resistance is the hindrance of flow against the current.

When a voltage is supplied to a conductor, it creates an electric field E inside it, which causes the charges to move. The amount of current that develops is determined by the material and the electric field that is formed. This density can be somewhat complicated, but it can be calculated using reasonable assumptions, such as the metals being at room temperature.