Electrical Engineering Materials Lecture Notes Quiz

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Questions and Answers

What are the factors affecting the resistivity of electrical materials?

Temperature, impurities, and crystal structure

What is the motion of an electron in an electric field?

The electron experiences drift

What is the equation of motion of an electron?

Newton's second law of motion

What is thermionic emission?

The emission of electrons from metals due to heat Signup and view all the answers

What is the significance of the loss tangent in dielectric materials?

It indicates the amount of energy lost as heat Signup and view all the answers

What are the dielectric properties of polymeric systems?

Polymeric systems exhibit frequency and temperature dependence of the dielectric constant Signup and view all the answers

What are the three types of magnetic materials discussed in the text?

Diamagnetism, paramagnetism, ferromagnetism Signup and view all the answers

Which material has the highest electrical conductivity?

Silver Signup and view all the answers

What is the next most conductive material after silver?

Copper Signup and view all the answers

Why is aluminium becoming more important as a conductor material?

It is light and has high conductivity Signup and view all the answers

Why does gold not find use in the electrical industry?

It is expensive Signup and view all the answers

What is superconductivity?

Vanishing resistivity at absolute zero Signup and view all the answers

What is the effect of temperature on the electrical resistance of most metals?

Increases with temperature Signup and view all the answers

What effect does alloying have on the electrical conductivity of a solid solution alloy?

Drops off rapidly with increased alloy content Signup and view all the answers

How does cold work affect the conductivity of a metal?

Decreases the conductivity Signup and view all the answers

What is the effect of age hardening on the resistivity of an alloy?

Increases the resistivity Signup and view all the answers

Study Notes

Factors Affecting Resistivity

Temperature: Increased temperature generally increases resistivity in most materials (metals), impacting electron movement and collisions.
Impurities: Adding impurities like carbon to iron increases resistivity, hindering electron flow.
Grain Size: Smaller grain sizes increase resistivity due to more grain boundaries, which act as obstacles to electron movement.
Defects: Dislocations and other defects introduce scattering points, impacting electron flow and increasing resistivity.

Electron Motion in an Electric Field

Electrons are negatively charged and move in a direction opposite to the electric field.

Equation of Motion

The equation of motion of an electron in an electric field can be derived using Newton's second law:
- F = ma (Force equals mass times acceleration)
- Where F is the force due to the electric field, m is the mass of the electron, and a is the acceleration.

Thermionic Emission

Thermionic emission occurs when electrons gain sufficient thermal energy to overcome the work function of a material and escape into the surrounding space.
This process plays a vital role in electronic devices like vacuum tubes.

Significance of Loss Tangent

The loss tangent (tan delta) in dielectric materials measures energy dissipation or loss.
It describes the ratio of conductive current to capacitive current.
A lower loss tangent indicates a better dielectric material with less energy loss.

Dielectric Properties of Polymeric Systems

Polymeric materials commonly serve as dielectrics in capacitors.
Their dielectric strength, permittivity, and loss tangent are important properties.

Types of Magnetic Materials

Diamagnetic: These materials weakly oppose an applied magnetic field.
Paramagnetic: These materials are weakly attracted to an applied magnetic field.
Ferromagnetic: These materials have strong magnetization and attract magnetic fields.

Highest Electrical Conductivity

Silver (Ag) holds the highest electrical conductivity amongst all materials.

Second Most Conductive Material

Copper (Cu) is the second most conductive material after silver.

Aluminium as a Conductor

Aluminium (Al) is becoming a leading conductor material due to its:
- Lower cost compared to copper
- Lighter weight
- Good electrical conductivity

Gold's Limited Use in Electrical Industry

Gold is chemically inert and a good conductor but its high cost makes it unsuitable for applications requiring large quantities.

Superconductivity

Superconductivity refers to the ability of certain materials to conduct electricity with zero resistance below a critical temperature.
Superconductors offer potential applications in high-speed trains, power transmission, and magnetic resonance imaging (MRI).

Temperature Effect on Resistance

For most metals, electrical resistance increases with rising temperature.
Increased electron scattering due to thermal vibrations contributes to this effect.

Alloying and Conductivity

Alloying typically decreases electrical conductivity.
The presence of impurity atoms in the alloy disrupts the regular lattice structure, increasing electron scattering.

Cold Work and Conductivity

Cold work (deformation at lower temperatures) decreases conductivity.
It increases the number of defects and boundaries within the material, hindering electron flow.

Age Hardening and Resistivity

Age hardening increases resistivity.
This process involves the precipitation of second-phase particles that enhance the material's strength but also impede electron movement.

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Description

Test your knowledge of electrical engineering materials with this quiz based on lecture notes for Bachelor of Technology in Electrical Engineering at Veer Surendra Sai University of Technology. The quiz covers topics such as conductivity of metals, factors affecting resistivity, and motion of electrons in materials.