Interpretation Of Electrical Resistance And Conductance

Electric circuit resistance is analogous to gravity. You will soar out if there were no gravity. And you can’t leap if there’s too much of it. A short circuit occurs when there is low resistance to current flow. The current flow will be unaffected. Any current flow is impeded by excessive resistance. Many students do not understand the difference between electrical resistance and conductance. Mostly they remain sceptical about this subject. The same happens in the case of electrical resistivity and conductivity. However, these are somewhere related to electricity. Still, it is essential to understand the relationships and differences between these entities. 

What are Electrical Resistance and Electric Resistivity?

The property of an object that opposes the current flow through it is called electric resistance. Or you can say the force that slows the current flow rate or creates a hazard in its operation is the resistance of that particular object. Let’s understand it with Ohm’s Law.

Ohm’s Law

Whenever we solve an electric circuit, we generally use Ohm’s Law. According to this law, whatever current flows through a conductor is directly proportional to the potential or voltage difference applied to both its ends. 

Mathematically, we can write it as:

V ∝ I

Or V= RI.

Hence, R=V/I.

Now, you can say that the resistance of a conductor is the fraction of the potential difference and the current flow through it. Ohm’s Law states that resistance is inversely proportional to the current flow. The more the resistance, the less will be the current flow. The unit of resistance is Ohm. 

1-ohm resistance is the force generated in the circuit when the voltage difference across the course is 1 Volt, and the flowing current amount through the circuit is 1 Ampere.

The electrical resistance depends on the nature of the material, its dimensions, and the circuit’s temperature.

The property of a material that opposes current flow is the electric resistance of that conducting material. 

Let’s understand it in detail. 

The resistance of any content or conductor depends on the length of the circuit or wire. 

Since the current flow happens in any circuit due to the flow of free electrons, if the size of the wire is more, the electrons will take more time to reach the subsequent end of the wire. It is due to the collisions between them. So, if the length of the wire is more, the electricity has to face more resistance while passing through it.

You can say that the resistance of the wire is directly proportional to its length.

R∝l

The electric resistance of a wire is inverse to its cross-sectional area. A larger size provides ample space to move free electrons quickly, so there will be less opposition to current.

R∝1/A

Or R∝l/A

Or R= ⍴l/A

Here ⍴ is the proportionality constant, which is termed the material’s resistivity. So, electric resistivity is the resistance of a conductor having unit length and unit cross-sectional area. In other words, the resistance of a wire with a 1-metre length and one meter² cross-sectional area describes its resistivity. The SI unit of resistivity is Ohm metre.

Electric resistivity is independent of the shape and size of the conductor. Different materials have different resistivity. Insulators hold the highest resistivity. The next is alloy, and then comes semiconductors. Conductors have the most negligible resistivity. The formula for electric resistivity is stated below:

⍴=m/ne²𝞃,

⍴∝1/n means the resistivity of any material decreases if the number of free electrons increases. 

⍴∝1/𝞃 means the electrical resistivity is in anti relation to relaxation time 𝞃. 𝞃 depends on the temperature so that when temperature increases, 𝞃 decreases. Hence, we can also say that the resistivity or resistance of any conductor is in linear relation to temperature. As the temperature increases, resistivity or resistance also increases.

What are Electrical Conductance and Conductivity?

The electrical resistivity and conductivity of materials are essential properties. They differ in values in different materials. The conductivity of a material is determined by its transport qualities of electricity. You can measure it in various ways with a range of devices. When electricity flows freely through a substance, it is said to have high conductivity. Aluminium and copper have excellent conductivity. Electrical conductivity is the measurement of how easily electricity passes through it.

In simple words, the electric resistivity and conductivity are reciprocal or inverse to each other. We can denote the electric conductivity with σ. Here we can say that:

Electric conductivity σ=1/⍴

The SI unit of electric conductivity is 1/(mΩ) or ℧(mho)/m.

The electric conductance is inverse or reciprocal of the electric resistance. We can symbolically represent the conductance by the symbol G. The conductance formula is G=1/R.

You can measure the electric conductance in the SI unit mho(℧) or the 1/Ω.

The capacity of a solution to carry an electrical current is known as electrical conductance (or electrical conductivity). A direct current does not flow via two electrodes inserted into purified water. However, an electrical current flows through the salt solution if the solution contains electrolytes.

Electric Resistivity And Conductivity: Differences

Electric resistivity and conductivity differ in the following ways:

Electrical Resistivity

1. The symbol of resistivity is ⍴.

2. The SI unit of resistivity measurement is Ohm-metres (Ωm).

3. It is the property of a material that opposes the flow of free electrons or current flow.

Electrical Conductivity

1. The symbol of conductivity is σ.

2. The SI unit of conductivity is Siemens (℧(mho)/m).

3. The materials’ property supports the flow of free electrons or current flow.

Conclusion

Thus, you can see that all the four entities are co-related to each other. Here, the resistance and the conductance are the forces that oppose and support the electricity flow across a circuit. The electrical resistivity and conductivity are material properties that restrict and allow the circuit’s current flow. The difference is quite simple and easy to understand.