Drift Velocity And Resistance - Why Ohm’S Law Is Good

Slide 1: Drift Velocity and Resistance - Why Ohm’s Law is Good

In a conductor, current is the flow of charged particles.
Drift velocity refers to the average velocity of charged particles in a conductor.
Resistance is the measure of opposition to the flow of current.
Ohm’s Law relates current, voltage, and resistance.
Ohm’s law states that the current flowing through a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.

Slide 2: Definition of Drift Velocity

Drift velocity is the average velocity of charged particles, such as electrons, in a conductor when a current flows.
It is generally very low, typically on the order of millimeters per second.
Drift velocity depends on the strength of the electric field, the charge of the particles, and the particle mobility.

Slide 3: Factors Affecting Drift Velocity

Drift velocity is affected by:

Electric field strength: Higher the electric field strength, higher the drift velocity.
Charge of the particles: Greater the charge, greater the drift velocity.
Particle mobility: Higher the mobility, higher the drift velocity.

Slide 4: Definition of Resistance

Resistance is a measure of how much a material or component opposes the flow of electric current.
It is denoted by the symbol R and measured in ohms (Ω).
Resistance depends on the material, length, cross-sectional area, and temperature of the conductor.

Slide 5: Ohm’s Law Equation

Ohm’s Law can be expressed using the equation: V = I * R

V represents the voltage across the conductor in volts (V).
I represents the current flowing through the conductor in amperes (A).
R represents the resistance of the conductor in ohms (Ω).

Slide 6: Relationship between Current and Voltage

According to Ohm’s Law, the current flowing through a conductor is directly proportional to the voltage applied across it.
Doubling the voltage will result in a doubling of the current, given that the resistance remains constant.
Similarly, reducing the voltage will reduce the current.

Slide 7: Relationship between Current and Resistance

According to Ohm’s Law, the current flowing through a conductor is inversely proportional to the resistance of the conductor.
Doubling the resistance will result in halving the current, given that the voltage remains constant.
Similarly, reducing the resistance will increase the current.

Slide 8: Proportional Relationship between Voltage and Resistance

Voltage and resistance have a direct proportional relationship according to Ohm’s Law.
Increasing the voltage across a conductor will result in an increase in the current if the resistance remains constant.
Similarly, reducing the voltage will reduce the current.

Slide 9: Examples of Ohm’s Law Application

Example 1: A conductor has a resistance of 10 Ω and a voltage of 5 V is applied. Calculate the current flowing through the conductor. `` V = I * R

5V = I * 10Ω I = 0.5 A Example 2: If the current flowing through a conductor is 2 A and the resistance is 8 Ω, calculate the voltage. V = I * R V = 2A * 8Ω V = 16V ``

Slide 10: Conclusion

Ohm’s Law provides a fundamental relationship between voltage, current, and resistance in a conductor.
It helps us understand the behavior of electrical circuits and how different parameters are related.
Ohm’s Law forms the foundation for many electrical calculations and is essential in analyzing and designing circuits.

Factors Affecting Resistance

Length of the conductor: Longer the conductor, higher the resistance.
Cross-sectional area of the conductor: Smaller the cross-sectional area, higher the resistance.
Material of the conductor: Different materials have different resistivities, which affect resistance.
Temperature of the conductor: Higher temperatures increase resistance due to increased atomic vibrations.

Resistivity and Conductivity

Resistivity (ρ) is a property of a material that determines its resistance.
Resistivity is measured in ohm-meters (Ω·m).
Conductivity (σ) is the reciprocal of resistivity, measured in siemens per meter (S/m), and indicates how conductive a material is.
The relationship between resistivity, conductivity, and resistance is given by the equation: R = ρ * (L / A) or σ = 1 / ρ, where R represents resistance, L represents length, and A represents cross-sectional area.

Power Dissipation

Power (P) is the rate at which work is done or energy is transferred.
In an electrical circuit, power is dissipated as heat due to the resistance of the conductor.
The power dissipation in a resistor is given by the equation: P = I^2 * R or P = (V^2) / R, where P represents power, I represents current, V represents voltage, and R represents resistance.

Units of Power and Energy

Power is measured in watts (W).
Energy is the integral of power over time.
Energy is measured in joules (J).
The relationship between power and energy is given by the equation: E = P * t, where E represents energy, P represents power, and t represents time.

Ohmic and Non-Ohmic Conductors

Ohmic conductors obey Ohm’s Law, where the current is directly proportional to the voltage and inversely proportional to the resistance.
Examples of ohmic conductors include most metals and conductive solutions.
Non-ohmic conductors do not obey Ohm’s Law and have varying resistance with applied voltage or current.
Examples of non-ohmic conductors include semiconductor diodes and gas discharge tubes.

Temperature Dependence of Resistance

For most metals, resistance increases with an increase in temperature.
This is due to the increased frequency of atomic vibrations, which obstruct the flow of conducting electrons.
Some materials, like semiconductors, have a decrease in resistance with increasing temperature due to other effects like electron mobility changes.

Superconductivity

Superconductivity is a phenomenon where certain materials exhibit zero electrical resistance below a critical temperature.
Superconductors can conduct large currents without any power loss.
Theories explaining superconductivity involve Cooper pairs of electrons and the exclusion of magnetic fields from the material.

Applications of Ohm’s Law

Ohm’s Law is widely used in various electrical and electronic applications, including:
1. Designing and analyzing circuits.
2. Power distribution systems.
3. Electrical appliances and devices.
4. Electronic components and circuits.
5. Electric vehicles and renewable energy systems.

Limitations of Ohm’s Law

Ohm’s Law assumes that the material under consideration is homogeneous and linear.
It does not account for non-linear effects, such as temperature dependence or non-ohmic behavior.
Other factors like junctions, capacitance, and inductance can influence circuit behavior, beyond the scope of Ohm’s Law.

Summary

Ohm’s Law provides a fundamental relationship between voltage, current, and resistance.
Resistance depends on factors like material, length, cross-sectional area, and temperature.
Power dissipation, units of power and energy, ohmic and non-ohmic conductors, temperature dependence, and superconductivity are important concepts related to resistance.
Ohm’s Law finds wide application but has limitations in dealing with non-linear and complex circuits. Sure! Here are slides 21 to 30 for your 12th Boards Physics lecture on “Drift Velocity and Resistance - Why Ohm’s Law is Good”:

Factors Affecting Drift Velocity

Electric field strength: Higher the electric field strength, higher the drift velocity.
Charge of the particles: Greater the charge, greater the drift velocity.
Particle mobility: Higher the mobility, higher the drift velocity.

Definition of Resistance

Resistance is a measure of how much a material or component opposes the flow of electric current.
It is denoted by the symbol R and measured in ohms (Ω).
Resistance depends on the material, length, cross-sectional area, and temperature of the conductor.

Ohm’s Law Equation

Ohm’s Law can be expressed using the equation: V = I * R.
V represents the voltage across the conductor in volts (V).
I represents the current flowing through the conductor in amperes (A).
R represents the resistance of the conductor in ohms (Ω).

Relationship between Current and Voltage

According to Ohm’s Law, the current flowing through a conductor is directly proportional to the voltage applied across it.
Doubling the voltage will result in a doubling of the current, given that the resistance remains constant.
Similarly, reducing the voltage will reduce the current.

Relationship between Current and Resistance

According to Ohm’s Law, the current flowing through a conductor is inversely proportional to the resistance of the conductor.
Doubling the resistance will result in halving the current, given that the voltage remains constant.
Similarly, reducing the resistance will increase the current.

Proportional Relationship between Voltage and Resistance

Voltage and resistance have a direct proportional relationship according to Ohm’s Law.
Increasing the voltage across a conductor will result in an increase in the current if the resistance remains constant.
Similarly, reducing the voltage will reduce the current.

Examples of Ohm’s Law Application Example 1: A conductor has a resistance of 10 Ω and a voltage of 5 V is applied. Calculate the current flowing through the conductor.

V = I * R
5V = I * 10Ω
I = 0.5 A Example 2: If the current flowing through a conductor is 2 A and the resistance is 8 Ω, calculate the voltage.
V = I * R
V = 2A * 8Ω
V = 16V

Conclusion

Ohm’s Law provides a fundamental relationship between voltage, current, and resistance in a conductor.
It helps us understand the behavior of electrical circuits and how different parameters are related.
Ohm’s Law forms the foundation for many electrical calculations and is essential in analyzing and designing circuits.

Factors Affecting Resistance

Length of the conductor: Longer the conductor, higher the resistance.
Cross-sectional area of the conductor: Smaller the cross-sectional area, higher the resistance.
Material of the conductor: Different materials have different resistivities, which affect resistance.
Temperature of the conductor: Higher temperatures increase resistance due to increased atomic vibrations.

Resistivity and Conductivity

Resistivity (ρ) is a property of a material that determines its resistance.
It is measured in ohm-meters (Ω·m).
Conductivity (σ) is the reciprocal of resistivity, measured in siemens per meter (S/m), and indicates how conductive a material is.
The relationship between resistivity, conductivity, and resistance is given by the equation: R = ρ * (L / A) or σ = 1 / ρ, where R represents resistance, L represents length, and A represents cross-sectional area.