Conductors, Semiconductors And Insulators - Energy Levels & Current Flow In Wire

Conductors, Semiconductors and Insulators - ENERGY LEVELS & CURRENT FLOW IN WIRE

Conductors, semiconductors, and insulators are types of materials based on their ability to conduct electric current.
Conductors have low resistance and readily allow the flow of electric current.
Examples of conductors include metals like copper and aluminum.
Semiconductors have moderate resistance and their conductivity can be modified.
Examples of semiconductors include silicon and germanium.
Insulators have high resistance and do not allow the flow of electric current.
Examples of insulators include rubber, plastic, and wood.

Energy Levels in Atoms

In an atom, electrons are arranged in energy levels or shells.
The innermost energy level is closest to the nucleus and has the lowest energy.
The outermost energy level is farthest from the nucleus and has the highest energy.
Electrons occupy the lowest available energy levels.
Each energy level can hold a certain number of electrons:
- First energy level: 2 electrons
- Second energy level: 8 electrons
- Third energy level: 8 electrons (can hold more if there are more energy levels)

Valence Electrons

Valence electrons are the electrons in the outermost energy level of an atom.
The number of valence electrons determines the chemical properties of an element.
For example, elements in the same group of the periodic table have the same number of valence electrons.
Valence electrons are involved in forming chemical bonds and determining the conductivity of materials.
In conductors, valence electrons are loosely bound and can move freely, allowing the flow of electric current.

Current Flow in a Wire

When a voltage is applied across a conductor, a current flows through it.
The flow of electric current is due to the movement of electrons.
Electrons move from the negative terminal to the positive terminal, creating a current flow.
The direction of the current flow is opposite to the direction of electron flow.
This convention is known as the “conventional current flow” and is used in circuit analysis.

Electronic Conduction in Metals

In metals, valence electrons are loosely bound and can move freely.
These free electrons are responsible for the high conductivity of metals.
When a voltage is applied, the free electrons accelerate and drift in the direction of the electric field.
Collisions with other particles in the metal cause the free electrons to lose some of their energy.
However, they gain energy from the electric field, resulting in a net drift velocity and current flow.

Energy Bands in Solids

In solids, the energy levels of individual atoms combine to form energy bands.
Valence band: The highest energy band filled with electrons at absolute zero temperature.
Conduction band: The next higher energy band that is empty (or partially filled) at absolute zero temperature.
The energy gap between the valence and conduction bands is known as the band gap.
The band gap determines the conductive properties of a material (conductor, insulator, or semiconductor).

Conductors and Energy Bands

In conductors, the valence and conduction bands overlap.
This overlap allows valence electrons to move into the conduction band easily.
The presence of available energy states in the conduction band allows for efficient electron flow in conductors.
The mobility of electrons in conductors contributes to their high electrical conductivity.
The Fermi level represents the highest occupied energy level in a conductor at absolute zero temperature.

Insulators and Energy Bands

In insulators, the energy gap between the valence and conduction bands is large.
This large energy gap makes it difficult for electrons to move from the valence band to the conduction band.
Insulators have few available energy states in the conduction band, hindering electron flow and making them poor conductors.
The valence band is completely filled, and the conduction band is empty at absolute zero temperature in insulators.

Semiconductors and Energy Bands

Semiconductors have a smaller energy gap compared to insulators.
The energy gap in semiconductors can be modified by applying external influences such as temperature or doping.
At absolute zero temperature, the valence band is full and the conduction band is empty in semiconductors.
With an increase in temperature or doping, some electrons can be excited to the conduction band, allowing for current flow.
Semiconductor devices utilize this property to control and manipulate electric current.

Slide 11

The conductivity of a material can be determined by its resistivity.
Resistivity is a property that quantifies a material’s ability to oppose the flow of electric current.
It is denoted by the symbol ρ (rho).
Resistivity is measured in ohm-meters (Ω∙m).
Resistivity is used to calculate the resistance of a conductor using the formula: R = ρ * (L/A)
- where R is the resistance, L is the length of the conductor, and A is the cross-sectional area.

Slide 12

Ohm’s Law relates the voltage (V), current (I), and resistance (R) in a conductor.
Ohm’s Law states that the current flowing through a conductor is proportional to the voltage applied across it, and inversely proportional to the resistance.
The equation for Ohm’s Law is: V = I * R
This equation can be rearranged to solve for current (I) or resistance (R) when the other variables are known.

Slide 13

Conductivity (σ) is the reciprocal of resistivity.
It is a measure of how easily a material can conduct electric current.
Conductivity is calculated using the formula: σ = 1/ρ
Conductivity is typically measured in siemens per meter (S/m).
The higher the conductivity, the better the material is at conducting electric current.

Slide 14

In a wire, current flows due to the movement of free electrons.
When a voltage is applied across a wire, an electric field is established.
The electric field exerts a force on the free electrons, causing them to move.
The movement of electrons results in the flow of electric current in the wire.
The rate of flow of electric charge is defined as current, and it is measured in amperes (A).

Slide 15

The direction of current flow is opposite to the movement of electrons.
Conventionally, current is considered to flow from the positive terminal to the negative terminal.
This convention is known as the “conventional current flow” and is used in circuit analysis.
The actual flow of electrons, however, is from the negative terminal to the positive terminal.
It is important to note the difference between the conventional current flow and the electron flow.

Slide 16

Electric current is quantified using the concept of charge.
The unit of charge is the coulomb (C).
One coulomb is defined as the amount of charge that flows when a current of one ampere (1 A) flows for one second.
The charge flowing through a conductor can be calculated using the equation: Q = I * t
- where Q is the charge in coulombs, I is the current in amperes, and t is the time in seconds.

Slide 17

The flow of electric current can be visualized using the analogy of water flow in pipes.
Voltage can be compared to the pressure of water, which causes the flow.
Current can be compared to the rate of water flow, which is dependent on the pressure and the resistance of the pipe.
Resistance can be compared to the narrowness or obstructions in the pipe, which restrict the flow.

Slide 18

Conductance is the reciprocal of resistance.
It is a measure of how easily a material permits the flow of electric current.
Conductance is calculated using the formula: G = 1/R
Conductance is typically measured in siemens (S).
The higher the conductance, the better the material is at conducting electric current.

Slide 19

The conductance of a wire is directly proportional to its cross-sectional area.
A wider wire has more space for the electrons to flow, resulting in higher conductance.
The resistance of a wire is inversely proportional to its cross-sectional area.
A wider wire has less obstruction to the flow of electrons, resulting in lower resistance.
Therefore, a thicker wire has lower resistance and higher conductance compared to a thinner wire.

Slide 20

The length of a wire also affects its resistance.
Resistance is directly proportional to the length of the wire.
A longer wire provides more obstacles for the flow of electrons, resulting in higher resistance.
Therefore, a shorter wire has lower resistance compared to a longer wire.
When designing electrical circuits, it is important to consider the length and thickness of wires to optimize the flow of electric current.

Slide 21

The resistance of a wire can also be affected by its material.
Different materials have different resistivities, which determine their conductivity.
For example, copper has a lower resistivity compared to iron, making it a better conductor.
The resistivity of a material is determined by factors such as the number of free electrons and their mobility.

Slide 22

The temperature of a wire can also affect its resistance.
As the temperature increases, the resistance of most materials also increases.
This is due to the increased vibration of atoms, which hinders the flow of electrons.
The relationship between resistance and temperature can be described using the temperature coefficient of resistance (TCR).
TCR is calculated using the equation: TCR = (ΔR/R₀) / (ΔT/T₀)
- where TCR is the temperature coefficient of resistance, ΔR is the change in resistance, R₀ is the initial resistance, ΔT is the change in temperature, and T₀ is the initial temperature.

Slide 23

The resistance of a wire can be influenced by external factors such as magnetic fields.
A magnetic field perpendicular to the direction of current flow can induce an additional resistance known as magnetic resistance or magnetoresistance.
Magnetoresistance can occur in wires made of magnetic materials or when a wire is placed in a magnetic field.
This effect can be utilized in certain applications, such as magnetic sensors and magnetic storage devices.

Slide 24

The resistance of a wire can be modified by altering its dimensions or material properties.
For a given material, the resistance of a wire is directly proportional to its length and inversely proportional to its cross-sectional area.
Resistance can be calculated using the formula: R = ρ * (L/A)
- where R is the resistance, ρ is the resistivity of the material, L is the length of the wire, and A is the cross-sectional area of the wire.

Slide 25

In circuits, resistors are commonly used to control the flow of electric current.
A resistor is a passive two-terminal electrical component that restricts the flow of current.
The resistance of a resistor is determined by its material properties and dimensions.
Resistors are available in different resistance values, which are indicated by color codes.

Slide 26

Resistance in a circuit can be combined using series and parallel connections.
In a series connection, resistors are connected end-to-end, and the total resistance is the sum of the individual resistances.
In a parallel connection, resistors are connected side-by-side, and the total resistance is calculated using the reciprocal of the sum of the reciprocals of the individual resistances.
Resistance combinations can be used to achieve specific circuit requirements, such as voltage division or current limiting.

Slide 27

Superconductivity is a phenomenon observed in certain materials at very low temperatures.
Superconductors have zero electrical resistance, allowing for the flow of electric current without any energy losses through resistance.
Superconductivity is used in applications such as magnetic resonance imaging (MRI) and particle accelerators.
The discovery and understanding of superconductivity have led to groundbreaking advancements in physics and technology.

Slide 28

In conclusion, conductors, semiconductors, and insulators differ in their ability to conduct electric current based on their energy levels, band structures, and material properties.
Conductors have low resistance and high conductivity, allowing for the efficient flow of electric current.
Semiconductors have moderate resistance and their conductivity can be modified, making them suitable for electronic devices.
Insulators have high resistance and do not permit the flow of electric current.
Understanding the behavior of these materials is crucial for various applications in electrical and electronic systems.

Slide 29

It is important to consider the resistivity, dimensions, and material properties of conductors when designing electrical circuits.
The resistivity determines the resistance of the wire, which affects the flow of current.
Optimizing the dimensions and material properties of wires can ensure efficient current flow and prevent energy losses through unnecessary resistance.
Additionally, the temperature and external factors should be taken into account to accurately determine the resistance and performance of the circuit.

Slide 30

The study of conductors, semiconductors, and insulators is fundamental to understanding the behavior of electrical systems.
These materials play a crucial role in modern technology and contribute to the development of various devices and applications.
Advanced understanding of the electrical properties of different materials enables engineers and scientists to design innovative solutions that shape our world.