What is Electrical property?

The term "electrical property" refers to the behavior of a material in a specific electrical condition. Whenever electrical current flows in a material, the behavior of the material indicates the electrical properties. The electrical properties vary with respect to different types of materials. Some engineering materials have a better electrical property in comparison to others.

What are the importance of electrical properties of materials?

Whenever there is a requirement to transmit electric current from one place to another, there would be a need for a material with good electrical conductivity to transmit with minimum loss. Suppose there is a need for quick heating of material under the flow of electricity. In that case, there should select a material that has more electrical resistance and the ability to convert electrical energy to thermal energy.

Electrical properties of materials

Engineering materials have different electrical properties that are very useful in selecting materials for different purposes, and conditions are given below in the following steps.

Electrical resistivity

It is a very important property with a wide range of applicability in the context of the selection of engineering materials. This property of material offers resistance against the flow of current. If the value of resistivity of a material is more, it means the current flow would be less. To increase the current flow in the material, it should have low resistivity.

Electrical conductivity

It is another property of a material that decides the rate of flow of current. If the rate of current flow in a material is more, it means the value of conductivity of material would be more. The value of electrical conductivity helps obtain the value of water purity etc. The relation between electrical conductivity and electrical resistance is an inverse one.

The mathematical expression of electrical conductivity can be represented as,

$\sigma =\frac{1}{\rho }$

Here, $\sigma$ represents the electrical conductivity and $\rho$ represents the electrical resistivity.

Semi conductivity

It is the term generally used for semiconductors that have conductivity between the conductivity of the conductor and the conductivity of the insulator. This property is very useful and has a wide range of applications in the semiconductor industry.

Superconductivity

It is also a property of some engineering materials that offer no electrical resistance when it lies below the critical temperature. The temperature zone in which some materials show the property of superconductivity, the electrical conductivity value would be infinite.

Electrical resistance

Whenever an electric conductor wire employs to conduct a specific electric current between two ends points with the help of wire then the value of resistance of a wire can obtain with the help of the wire's resistivity, length and cross-sectional area of the wire. The expression of the electrical resistance can be represented as,

$R=\frac{\rho L}{A}$

Here, $R$ represents electrical resistance, $\rho$ represents electrical resistivity, $L$ represents the length of wire/conductor and $A$ represents the cross sectional area of wire.  

Dielectric strength

It is also a property of the material that represents the capacity to work under a high electric voltage. Normally this property is used for insulating material to represent the operating voltage. If the value of the dielectric strength of a material is more, it means the material can work under large electric voltage.

Temperature coefficient of resistance

The property of a material indicates the variation of electric resistance with respect to changes in the temperature of the material. The value of resistivity and conductivity of a material varies with temperature. If the value of the temperature of a conducting material increases, then the value of the material's conductivity will decrease.

The expression of electrical resistance of material in terms of temperature can be represented as,

$R=R_0\left(1+\alpha ∆T\right)$

Here, $R$ represents the electrical resistance with respect to temperature, $R_0$ represents the initial electrical resistance at room temperature, $\alpha$ represents the thermal coefficient and $∆T$ represents the change in temperature of material.

Thermoelectricity

A small voltage generation would occur whenever two different types of conducting wires connect ends to ends and are placed at a different temperature. This principle of voltage generation helps in the working of thermocouples and refers to the See-back effect. The pictorial representation of the Seeback effect is given below.

One more property of a material opposite to the Seeback effect refers to the Peltier effect. According to this effect, when two different metals connect end to end, and a specific voltage applies at the ends, then there would be an electric voltage generated. The pictorial representation of the Peltier effect is given below.

Electric conductivity of different type of materials

Based on the property of electric conductivity, materials can be classified into three parts: conductor, semiconductor, and insulator The basic concept of these types of materials are given below in the following steps.

Conductor

The value of conductivity of the conducting material is large compared to other types of material like semiconductors and insulators. The value of resistivity of the conductor would be less, and the conductivity would be high. Conductors are very useful for making the electric transformer and other electric equipment. For example, iron, silver, aluminum, etc.

Semiconductor

A semiconductor is also a material consisting of electrical conductivity lower than a conductor but higher than an insulator. There are also two types of conducting materials that are intrinsic and extrinsic. The intrinsic conductor is also referred to by the name pure conductor, and the extrinsic semiconductor refers to an impure conductor. For example, silicon and germanium.

Insulator

It is a class of material that is very useful to use between two conductors that do not allow the current flow through this material. The conductivity of the insulator is approximately equal to zero, whereas the value of resistivity is very large. Generally, insulators are used for insulation from electrical current. For example, plastic, rubber, glass, etc.

Some other electrical properties of materials

Some engineering materials have some other electrical properties like Ferroelectricity, Piezoelectricity, etc. that are given in the following steps.

Ferroelectricity

The property of a material that exhibits spontaneous polarization in the absence of an electric field and reverses back on the application of an electric field is called ferroelectricity. The value of the dielectric constant of a ferroelectric material is very high. An example of the material is barium titanate, etc.

Piezoelectricity

The property of materials that can convert the electric form of energy into mechanical form refers to piezoelectricity. The mechanical output is in the form of strain. The materials that have this property refers as piezoelectric material. The basic use of these materials is in microphones, speakers, etc.

Measurement of electrical properties of materials

Different electrical properties of the materials can measure with the help of the different devices which are given in the following steps.

Electric resistance

The value of electric resistance of a conducting electrical wire can be obtained with the help of Ohmmeter. When a specific current runs in the wire with a particular applied electric voltage, then the value of resistance of a wire can obtain with the help of Ohm's law.

Electrical conductivity

The value of electrical conductivity of a conducting medium can obtain with the help of EC meter. The value of conductivity of a conductor is very high compared to the conductivity of a semiconductor.

Electric current

The value of the electric current that flows in a conductor can obtain with the help of a device refers as an ammeter. If the value of resistance of a conductor is less then the value of current flow in the conductor would be more.

Common Mistakes

• Students sometimes get confused regarding the variation of electrical conductivity of a conductor and a semiconductor. However, the value of electrical conductivity will decrease with an increase in temperature, whereas the electrical conductivity of a semiconductor will increase with an increase in temperature.
• Sometimes, students also get confused about the relation between electrical resistivity and electrical conductivity. However, the relation between electrical resistivity and electrical conductivity is an inverse one.
• The student also gets confused about the thermoelectric effects, See-back, and Peltier effects. However, thermocouple works on the principle of the See-back effect, whereas the Peltier effect is just opposite to See-back effect.

Context and Applications

Electrical properties of materials are very significant in the several professional exams and courses for undergraduate, Diploma level, graduate, postgraduate. For example:

• Bachelor of Technology in Mechanical Engineering
• Bachelor of Technology in Electrical Engineering
• Bachelor of Technology in Civil Engineering
• Master of Technology in Mechanical Engineering
• Doctor of Philosophy in Mechanical Engineering
• Diploma in Mechanical and Electrical Engineering

Related Concepts

• Intrinsic conductivity
• Extrinsic conductivity
• Effect of impurities on conductivity
• Effect of temperature on conductivity
• Effect of plastic deformation on conductivity
• Fermi level
• Application

Practice Problems

Q 1. What is the property which resists/obstructs the flow of electricity?

a. Conductivity

b. Dielectric strength

c. Thermoelectricity

d. Resistivity

Correct option: (d)

Q 2. Which of the following option shows the formula of electrical resistance?

a. $R=\frac{\rho L}{A}$

b. $R=\frac{\rho L}{2A}$

c. $R=\frac{2\rho L}{A}$

d. All of these

Correct option: (a)

Q 3. Which of the following shows the working principle of thermocouple?

a. Seeback effect

b. Peltier effect

c. Thomson effect

d. None of these

Correct option: (a)

Q 4. Which one represents the capacity of a material against high voltage?

a. Thermoelectricity

b. Dielectric strength

c. Electrochemical effect

d. Electromechanical effect

Correct option: (b)

Q 5. The coefficient of resistance of an insulator can be represented by

a. Negative

b. Positive

c. Infinite

d. Zero

Correct option: (c)