Factors affecting Resistance, Inductance, and Capacitance

Resistance, inductance, and capacitance are three main parameters of an electric circuit.

Resistance is defined as the measure of opposition in the flow of electric current. Inductance is defined as the measure of opposition in change in the direction and magnitude of the current. Whereas, capacitance is defined as the measure of opposition in change in the voltage.

The resistance, inductance, and capacitance of a conductor depend on several factors like temperature, length, cross-sectional area, etc. In this article, we will discuss about all these factors affecting the resistance, inductance, and capacitance of a conductor.

What is Resistance?

In electrical engineering, resistance is the measure of opposition that the material of a conductor offers in the flow of electric current. Therefore, the resistance is also known as electric friction. It is measured in Ohms, denoted by $\mathrm{\Omega }$.

For a conductor having lm length, $\mathrm{am^2}$ cross-sectional area, and $\mathrm{\rho }$ resistivity, the resistance is given by,

$$\mathrm{R\:=\:\rho \frac{l}{a}}$$

Factors Affecting Resistance

From the above equation, we can see that the resistance of a conductor depends on the following factors −

Length - The resistance of a conductor is directly proportional to length of the conductor. Thus, a longer conductor will have a higher resistance and vice-versa.

Cross-Sectional Area - The resistance of a conductor is inversely proportional to the area of cross-section of the conductor. Therefore, a conductor having a large cross-sectional area will have a lower resistance and vice-versa.

Nature of Material (Resistivity) - The resistance of a conductor also depends on the nature of material or resistivity or specific resistance. For example, a metallic conductor has a very low resistance while an insulator has a very high resistance.

These are the three most significant factors that affect the resistance of a conductor. Apart from these three factors, the following are some other important factors that affect the resistance of a conductor.

Temperature - The resistance of a material/conductor is also affected by the change in temperature. For metallic conductors, the resistance increases with increase in the temperature. For insulating or semiconductor materials, the resistance decreases with rise in temperature.

Frequency of AC Supply - When a conductor is subjected to alternating current supply, then its resistance changes with the frequency of the AC supply. This variation in resistance is due to skin effect and proximity effect of the AC supply. At very high frequency, the resistance of the conductor becomes significantly high.

Impurities - The impurities present in the material of the conductor also affects its resistance. This is due to the fact that impurities influence the flow of electric charge through the conductor. In a metallic conductor, impurities increase the resistance, while in semiconductors, the impurities are added to reduces their resistance.

Therefore, the resistance of a conductor is affected by several different factors. While designing electrical circuits, we need to consider all these factors affecting resistance to ensure the reliable operation of the circuits.

What is Inductance?

In electrical engineering, inductance is a property of an electrical conductor which opposes any change in the flow of electric current through it.

According to electromagnetic field theory, when an electric current is made to flow through a conductor, it creases a magnetic field around the conductor. This effect is known as magnetic effect of electric current.

The generated magnetic field changes with any change in the electric current. For example, the intensity of magnetic field becomes lower with the decrease in the current and vice-versa.

According to Faraday’s law of electromagnetic induction, the change in magnetic field induces an emf in the conductor which opposes the change in current. This is how the concept of inductance comes into picture.

For a conductor coil, the inductance is generally given by the following formula,

$$\mathrm{L\:=\:\frac{N^2\mu a}{l}}$$

Where, L represents the inductance of conductor coil measured in Henry, µ is the permeability of core material, a is the area of cross-section of coil, and l is the length of the coil.

Factors Affecting Inductance

From the above formula, we can observe that the following are the important factors that affect the inductance of a conductor or a coil -

Number of Turns - The inductance of a conductor or a coil is affected by the number of turns in it. Therefore, a conductor coil having a greater number of turns will have a higher inductance and vice-versa.

Length - The inductance of a coil is inversely proportional to its length. Thus, a longer coil will have a smaller inductance and vice-versa.

Area of Cross-Section - From the above formula, it can be seen that the inductance of the coil is directly proportional to the area of cross-section. Therefore, a coil having a larger cross-sectional area will have a higher inductance and vice-versa.

Permeability of Core Material - The inductance of a coil is also affected by the material of the core. As we can see in the formula, the inductance of the coil is directly proportional to the permeability of the core material. Thus, a coil having a core material of high permeability will have a high inductance.

All these are the key factors that affect the inductance of a coil/conductor significantly. Apart from these factors, the following are some other important factors that affect the inductance.

Shape of Coil - The shape of the coil greatly affects its inductance. This is due to the fact that different shapes of the coil have a different distribution of the magnetic flux.

Frequency of AC Supply - Inductance also changes with the variation in the frequency of alternating current supply.

Temperature - The inductance of a conductor is also affected by the temperature. This is due to the fact that the change in temperature of the inductor changes its magnetic characteristics like permeability of magnetic core.

This is all about inductance and factors affecting the inductance of a conductor coil. Let us discuss the factors affecting capacitance.

What is Capacitance?

The property of an electrical element that opposes any change in the voltage is referred to as capacitance.The circuit element that exhibits capacitance is called a capacitor.

A typical capacitor consists of two parallel plates made up of metal and these plates are separated by an insulating or dielectric material.

The capacitance of a capacitor is given by the following formula,

$$\mathrm{C\:=\:\varepsilon \frac{A}{d}}$$

Here, $\mathrm{\varepsilon}$ is the permittivity of the material placed between the plates, A is the cross-sectional area of each plate, and d is the distance between the plates.

The capacitance of a capacitor is measured in Farad (F), which is the SI unit of capacitance.

This is all about some basic facts related to capacitance. Let us now learn about different factors affecting capacitance.

Factors Affecting Capacitance

From the above equation of capacitance, we can see that the capacitance of a capacitor depends on the following main factors -

Nature of Dielectric Between Plates (Permittivity) - The permittivity or nature of dielectric material is one of the most significant factors that affects the capacitance of a capacitor. It can be seen that the capacitance of a capacitor is directly proportional to the permittivity of the material. Therefore, a capacitor having a dielectric material of high permittivity between its plates has a high capacitance and vice-versa.

Cross-Sectional Area of Plate - The capacitance of a capacitor is directly proportional to the cross-sectional area of plates. Therefore, if a capacitor has plates of large cross-sectional area will have a high capacitance and vice-versa.

Distance between Plates - From the equation, it is clear that the capacitance of a capacitor is inversely proportional to the distance between the plates. Therefore, a capacitor having large spacing between the plates will have a lower capacitance and vice-versa.

These are the most crucial factors that significantly affects the capacitance. However, there are several other factors that influence the capacitance, they are explained below.

Dielectric Strength - Dielectric strength is defined as the maximum voltage that a capacitor can handle without breaking down. Therefore, a capacitor having a high dielectric strength will have a higher capacitance and vice-versa.

Temperature - The variation in temperature can change the properties of the dielectric material between the plates of the capacitor. Therefore, the temperature also affects the capacitance.

Number of Plates - The capacitance of a capacitor also depends on the number of parallels plates used. Thus, a capacitor having a larger number of plates will have a higher capacitance and vice-versa.

So, this is all about capacitance and important factors affecting the capacitance.

Conclusion

In this article, we explained in detail the factors that affect the resistance, inductance, and capacitance of an electric circuit.

From the basic theory of electrical engineering, the resistance, inductance, and capacitance are the most fundamental parameters of an electric circuit. Therefore, it is important to know that what factors can change their values, which are explained in this article.

FAQs Related to Factors Affecting R, L, and C

The following are some commonly asked questions related to the factors affecting resistance, inductance, and capacitance.

1. What are 4 factors that affect resistance?

The following are the main 4 factors that affect the resistance of a conductor -

• Length of the conductor
• Area of cross-section of the conductor
• Nature of the material of the conductor
• Temperature

2. What is the biggest factor that affects resistance?

Resistivity or specific resistance or nature of material is the biggest factor that affects the resistance of a conductor.

3. What is the effect of resistance in a circuit?

In an electric circuit, resistance opposes the flow of electric current and converts the electrical energy into heat energy.

4. What is the formula for resistance?

The formula for calculating the resistance of a conductor is given by,

$$\mathrm{R\:=\:\frac{\rho l}{a}}$$

Where, $\mathrm{\rho}$ is resistivity, l is the length of conductor, and a is the area of cross-section.

5. What are the two factors affecting inductance of a conductor?

The two major factors that affect the inductance of a conductor are,

• Number of turns
• Permeability of magnetic material

6. What are three factors that determine the amount of inductance?

The inductance of a coil is determined by the following three factors -

• Number of turns in the coil
• Permeability of the core material
• Length of the coil

7. Does voltage affect capacitance?

No, voltage does not affect the capacitance of the capacitor, this is because the capacitance is a property which is entirely determined by the physical dimensions of the capacitor.

8. How does dielectric affect capacitance?

Dielectric is the material used between the plates of a capacitor. This dielectric material has an ability of polarization when subjected to an electric field. Hence, the measure of polarization of dielectric affects the capacitance of the capacitor.