General Electric System

1. Constituent parts of an electrical system (source, load, communication & control)

An electrical system consists of several key components that work together to generate, distribute, control, and manage electrical energy. The main constituent parts include:

Source: The source is where electrical energy originates. It could be a power plant, a generator, a battery, a solar panel, or any other device capable of producing electrical energy. The source provides the initial voltage and current to the system.

Load: The load is the component or device that consumes or utilizes the electrical energy. Loads can be categorized into two types:

i.Resistive Loads: These convert electrical energy into heat or light. Examples include incandescent bulbs, electric heaters, and toasters.

ii.Non-Resistive Loads: These convert electrical energy into other forms, such as mechanical energy (motors), electronic signals (computers), or light (LEDs).

Communication and Control: In modern electrical systems, communication and control components play a crucial role in ensuring efficient and safe operation. These components include:

Sensors: Sensors detect physical parameters like temperature, pressure, light, or motion. They provide feedback to control systems for making decisions.

Controllers: Controllers process information from sensors and determine the appropriate actions to be taken. They regulate voltage, current, and other system parameters.

Communication Networks: Communication systems enable devices and components to exchange data and information. This can include wired (Ethernet, CAN bus) or wireless (Wi-Fi, Bluetooth) communication protocols.

Programmable Logic Controllers (PLCs): PLCs are used for industrial automation and control. They can be programmed to execute specific tasks based on input conditions.

Protection and Safety Devices: Electrical systems require safeguards to prevent damage to components and ensure user safety. These devices include:

i.Fuses and Circuit Breakers: These devices interrupt the flow of current in case of a fault or overload, preventing damage to the system.

ii.Grounding and Earthing Systems: These systems provide a safe path for excess electrical energy to dissipate into the ground, reducing the risk of electric shock and fires.

Distribution System: The distribution system transports electrical energy from the source to the load. It includes:

i.Transformers: These devices change the voltage level for efficient transmission and distribution.

ii.Switchgear and Switchboards: These components control the flow of electricity and distribute it to various parts of the system.

iii.Power Conversion Devices: In some cases, electrical systems require the conversion of power from one form to another. This involves devices like inverters (DC to AC), rectifiers (AC to DC), and voltage regulators.

iv.Energy Storage: Energy storage systems, such as batteries or capacitors, store excess energy for later use or provide backup power during outages.

These constituent parts work together to create functional electrical systems that meet various needs, from powering households to running complex industrial processes. Proper design, operation, and maintenance of these components are essential for the reliable and safe functioning of electrical systems.

2. Current flow in circuit

Current flow in a circuit refers to the movement of electric charge through a closed path. This movement of charge is driven by an electric field created by a voltage difference (potential difference) across the circuit. Here's how current flow works:

1. Voltage Difference (Potential Difference): The flow of electric current is initiated by a voltage difference between two points in a circuit. Voltage is the driving force that pushes electric charges to move. It is often referred to as the "electromotive force" (EMF) or simply "voltage."

2. Conductor: To enable the flow of electric current, there must be a conducting path for the charges to move through. Conductors are materials that allow electric charges to move freely. Common conductors include metals like copper and aluminum.

3. Electric Charges: Electric current is the movement of electric charges. In most cases, the charges are electrons, which are negatively charged particles found in atoms.

4. Direction of Current: Conventionally, current is considered to flow from the positive terminal of a voltage source (like a battery) to the negative terminal. This convention was established before the understanding of electron flow, so in reality, electrons move from the negative terminal to the positive, opposite to the conventional current direction.

5. Flow of Electrons: When a voltage difference is applied across a circuit, electrons are pushed by the electric field. They move through the conductor from an area of higher potential (voltage) to an area of lower potential.

6. Closed Circuit: To maintain a continuous flow of current, the circuit must be closed or complete. In other words, there must be a complete loop for the charges to circulate. If the circuit is open (broken), no current can flow.

7. Current Measurement: The unit of electric current is the ampere (A). One ampere of current is defined as one coulomb of charge passing through a point in a circuit per second.

8. Ohm's Law: The relationship between voltage, current, and resistance is defined by Ohm's Law: V = I * R, where V is voltage, I is current, and R is resistance. This law explains how changes in voltage and resistance affect the current flow in a circuit.

9. Resistance: The opposition that a material offers to the flow of electric current is called resistance. It's measured in ohms (Ω). Different materials have different resistances, and components like resistors are used to control the amount of current flowing in a circuit.

In summary, electric current flows in a circuit when there is a voltage difference across a closed path, and electric charges (typically electrons) move through a conductor from an area of higher potential to an area of lower potential. The movement of charges is driven by the electric field created by the voltage source, and this flow of charges constitutes an electric current.

3. Electromotive force and potential difference

Electromotive Force (EMF) and Potential Difference (Voltage) are two fundamental concepts in the field of electrical engineering, crucial for understanding electric circuits, energy transfer, and electrical devices. Let's explore these concepts in depth:

1. Electromotive Force (EMF):

• EMF represents the energy per unit charge supplied by a source (like a battery) to move charges around a closed circuit.
• It's not a force in the mechanical sense but rather an energy supplier. EMF provides the potential energy necessary to move charges through a circuit.
• EMF is measured in volts (V).
• EMF takes into account both the energy provided by the source and the energy lost due to internal resistance, if present.
• For instance, a battery with an EMF of 9 volts provides 9 joules of energy to every coulomb of charge that passes through it.

2. Potential Difference (Voltage):

• Voltage, also known as potential difference, is the difference in electric potential between two points in a circuit.
• It measures the work done to move a unit charge from one point to another against the electric field's resistance.
• Voltage is what causes charges to move in an electric circuit. It's the driving force that accelerates charges through conductors and components.
• Voltage is also measured in volts (V).
• A potential difference of 1 volt between two points means that 1 joule of energy is required to move 1 coulomb of charge between those points.

Key Differences:

• EMF is associated with energy supply from a source, while potential difference is associated with energy consumption due to the presence of a load or resistance.
• EMF can be thought of as the total voltage generated by a source, whereas potential difference measures the voltage drop across a specific component or section of a circuit.
• EMF takes into account internal resistance and external load, while potential difference focuses on the voltage difference across specific points.
• EMF is the maximum voltage a source can provide, while potential difference represents the actual voltage applied across a circuit element.

Application:

• In a battery-powered circuit, the EMF of the battery sets the maximum voltage available. However, as current flows and encounters resistance, the potential difference (voltage drop) across components results in the actual voltage experienced by the load.

In summary, electromotive force (EMF) is the energy supplier that drives charges through a circuit, while potential difference (voltage) is the driving force that accelerates charges through a circuit. Both concepts are essential for understanding how electric circuits work, and they play a crucial role in designing and analyzing electrical systems and devices.

4. Electrical Units:

Electrical units are standardized measures used to quantify various properties and phenomena related to electricity and electrical circuits. Understanding these units is crucial for accurately describing and analyzing electrical systems. Here are some important electrical units:

Volt (V):
The volt is the unit of electrical potential difference and electromotive force.
It represents the amount of energy transferred per unit charge between two points in a circuit.
Symbol: V

Ampere (A):
The ampere is the unit of electric current.
It represents the rate of flow of electric charge past a point in a circuit.
Symbol: A

Ohm (Ω):
The ohm is the unit of electrical resistance.
It quantifies the opposition to the flow of electric current in a circuit.
Symbol: Ω

Watt (W):The watt is the unit of electrical power.It measures the rate at which energy is transferred or converted in a circuit.                                                                                                                       Symbol: W

Coulomb (C):
The coulomb is the unit of electric charge.
It represents the fundamental quantity of electric charge carried by a specific number of electrons.
Symbol: C

Farad (F):
The farad is the unit of electrical capacitance.
It quantifies a capacitor's ability to store electric charge per unit voltage.
Symbol: F

Henry (H):
The henry is the unit of electrical inductance.
It measures the ability of a component (like a coil) to store energy in a magnetic field.
Symbol: H

Hertz (Hz):
The hertz is the unit of frequency.
It represents the number of cycles or oscillations per second in an alternating current.
Symbol: Hz

Joule (J):
The joule is the unit of energy.
It quantifies the amount of work done or energy transferred in an electrical process.
Symbol: J

Watt-Hour (Wh):
The watt-hour is the unit of energy consumption or energy storage.
It represents the amount of energy consumed or stored when one watt of power is used or produced for one hour.
Symbol: Wh

Volt-Ampere (VA):
The volt-ampere is the unit of apparent power in an alternating current circuit.
It combines both the voltage and current magnitudes, accounting for phase differences.
Symbol: V

These units form the basis for quantifying various aspects of electrical systems, including voltage, current, resistance, power, energy, and more. They are essential for calculations, designs, and analyses in electrical engineering.

5. Ohm's Law

Ohm's Law is a fundamental principle in electrical engineering that describes the relationship between voltage, current, and resistance in an electrical circuit. It's named after the German physicist Georg Simon Ohm, who formulated this law in the 19th century. Ohm's Law states that:

"The current passing through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them."

Mathematically, Ohm's Law is represented by the equation:

V = I * R

Where:

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

Key points about Ohm's Law:

1. Direct Proportionality: The current through a conductor is directly proportional to the voltage applied across it, assuming the resistance remains constant. This means that increasing the voltage will lead to an increase in current, and vice versa.

2. Inverse Proportionality: The current through a conductor is inversely proportional to the resistance of the conductor, assuming the voltage remains constant. This means that increasing the resistance will lead to a decrease in current, and vice versa.

3. Linear Relationship: Ohm's Law applies to linear, ohmic conductors. In other words, the relationship between voltage, current, and resistance is a straight line on a graph.

4. Applicability: Ohm's Law is most accurate for metallic conductors at moderate temperatures. It may not hold true for non-linear components like diodes and transistors.

5. Units: It's crucial to ensure that the units are consistent when using Ohm's Law. Voltage is in volts (V), current is in amperes (A), and resistance is in ohms (Ω).

6. Power and Ohm's Law: Ohm's Law can be used in conjunction with power equations to determine how voltage, current, and resistance affect power dissipation in a circuit. The power equation is: P = I * V, where P is power in watts.

Ohm's Law is a foundational principle in electrical engineering and is used extensively for circuit analysis, design, and troubleshooting. It provides a clear understanding of how these three fundamental electrical quantities relate to each other within a circuit.

6. Resistor and Resistivity

Resistors:

Resistors are passive electronic components designed to introduce a specific amount of resistance into an electrical circuit. They are used to control current flow, divide voltage, limit current, and perform various functions in circuits. Here are key points about resistors:

1. Resistance Value (Ohms): Resistors are characterized by their resistance value, measured in ohms (Ω). This value determines how much the resistor impedes the flow of current in a circuit.

2. Color Code: For through-hole resistors, a color code is used to indicate their resistance value and tolerance. The color bands provide a quick visual way to identify the resistor's value.

3. Power Rating (Watts): Resistors also have a power rating, indicating how much power they can safely dissipate as heat. Exceeding the power rating can lead to overheating and failure.

4. Types of Resistors:

   • Fixed Resistors: These have a fixed resistance value and are the most common type.
   • Variable Resistors (Potentiometers and Rheostats): These allow manual adjustment of resistance.
   • Thermistors: These resistors have resistance that changes significantly with temperature.
   • Light-Dependent Resistors (LDRs): These resistors change resistance with varying light levels.

5. Series and Parallel: When resistors are connected in series, their resistances add up. When connected in parallel, their combined resistance is lower than the smallest individual resistance.

Resistivity:

Resistivity is a fundamental property of a material that quantifies how well it opposes the flow of electric current. It's a measure of the material's inherent resistance to current flow. Here's more about resistivity:

1. Definition: Resistivity (ρ) is the intrinsic property of a material that relates its resistance (R) to its dimensions and is given by the formula: ρ = R * A / L.

   • ρ: Resistivity in ohm-meter (Ω m).
   • R: Resistance in ohms (Ω).
   • A: Cross-sectional area of the material in square meters (m²).
   • L: Length of the material in meters (m).

2. Temperature Dependence: Resistivity often changes with temperature. Some materials have positive temperature coefficients (resistivity increases with temperature), while others have negative coefficients.

3. Factors Affecting Resistivity: Resistivity depends on factors like material composition, impurities, temperature, and crystal structure.

4. Relation to Conductivity: Conductivity (σ) is the reciprocal of resistivity (σ = 1 / ρ). Conductivity indicates how easily a material allows the flow of current.

5. Units: Resistivity is measured in ohm-meter (Ω m). It's important to note that it's a bulk property of a material, whereas resistance depends on both material properties and geometry.

6. Applications: Understanding resistivity is crucial in designing materials for specific applications, such as choosing the right wire for electrical transmission or designing components for specific resistance values.

In summary, resistors are components used to introduce controlled resistance into circuits, while resistivity is an intrinsic material property that defines how resistant a material is to current flow. Together, they play a significant role in designing, analyzing, and optimizing electrical circuits and systems.

7. Temperature Rise and Temperature Coefficient of Resistance

Temperature rise and temperature coefficient of resistance are important concepts in electrical engineering, particularly when dealing with materials and components that are sensitive to changes in temperature.

Temperature Rise:Temperature rise refers to the increase in temperature that occurs in a component or system when electrical current flows through it. When current passes through a resistor, for example, some of the electrical energy is converted into heat due to the resistance of the material. This heat energy raises the temperature of the component.Key points about temperature rise:

Power Dissipation: The heat generated in a component is proportional to the power dissipation, which is the product of current squared (I²) and resistance (R), following the formula P = I²R.

Heat Dissipation: Components are designed to handle a certain amount of power dissipation and, consequently, temperature rise. Excessive temperature rise can lead to component failure or reduced performance.

Heat Sinks and Cooling: In high-power applications, heat sinks and cooling mechanisms are used to dissipate excess heat and prevent components from reaching critical temperatures.

Thermal Resistance: Components have a thermal resistance parameter that indicates how efficiently they transfer heat. Lower thermal resistance values mean better heat dissipation.

Temperature Coefficient of Resistance:The temperature coefficient of resistance (TCR) is a parameter that quantifies how a material's resistance changes with temperature. It's expressed in fractional change of resistance per degree Celsius (°C) or Kelvin (K) change in temperature.

Mathematically, the TCR is given by:

TCR = (ΔR / R₀) / ΔT

Where:

ΔR: Change in resistance

R₀: Initial resistance at a reference temperature (usually 25°C)

ΔT: Change in temperature in degrees Celsius

Key points about temperature coefficient of resistance:

Positive and Negative TCR: If a material's resistance increases with temperature, it has a positive TCR. If resistance decreases with temperature, it has a negative TCR.

Materials with Positive TCR: Most conductors have positive TCR, meaning their resistance increases as temperature rises. This is important to consider when designing circuits that need stable resistance values.

Materials with Negative TCR: Some materials, like certain semiconductors, exhibit negative TCR. These materials can be used in applications where compensating for temperature changes is necessary.

Compensation: Understanding TCR is crucial for designing components that maintain stable resistance across varying temperatures. For example, precision resistors with low TCR are used in applications like temperature sensors.

In summary, temperature rise refers to the increase in temperature caused by power dissipation in components, while the temperature coefficient of resistance (TCR) quantifies how a material's resistance changes with temperature. These concepts are vital for ensuring the proper functioning and reliability of electronic systems across varying temperature conditions.

8. Voltage & current sources

Voltage and current sources are fundamental components in electrical circuits that provide electrical energy to the circuit. They play a crucial role in powering devices, creating bias conditions, and facilitating various circuit operations. Let's explore voltage and current sources in more detail:

Voltage Source:

A voltage source is a two-terminal component that maintains a constant voltage difference (potential difference) between its terminals, regardless of the current flowing through it. It supplies a specific voltage to the circuit, creating an electric field that drives current flow. Here are key points about voltage sources:

Ideal Voltage Source: An ideal voltage source provides a constant voltage regardless of the current it supplies. In reality, no source is perfectly ideal, but some sources come close under specific conditions.

Symbol: The symbol for a voltage source is typically represented as a circle with a plus (+) and minus (-) sign, indicating the positive and negative terminals.

Examples: Batteries, power supplies, and solar panels can be modeled as voltage sources.

Voltage Regulation: Some voltage sources are regulated to maintain a constant voltage even when the load changes. This is essential in applications where a stable voltage is required.

Current Source:

A current source is a two-terminal component that maintains a constant current through it, regardless of the voltage across its terminals. It provides a specific current to the circuit, ensuring that the current remains consistent. Here are key points about current sources:

Ideal Current Source: An ideal current source provides a constant current regardless of the voltage across it. Like voltage sources, ideal current sources are theoretical concepts.

Symbol: The symbol for a current source is usually represented as an arrow pointing away from the source, indicating the direction of current flow.

Examples: Current sources can be used in applications where a fixed current is required, such as biasing circuits or driving specific components.

Current Regulation: Some current sources are designed to maintain a constant current even when the load changes. These sources ensure that the desired current flows through the circuit.

Practical Considerations:

Internal Resistance: Real-world voltage sources often have internal resistance, affecting their ability to provide the full voltage across varying current demands.

Load Effects: The behavior of voltage and current sources can change based on the connected load. The load determines how the source's output voltage or current changes.

Combination: Voltage and current sources can be combined in circuits to achieve specific voltage-current relationships, depending on the circuit requirements.

In summary, voltage sources maintain a constant voltage across their terminals, while current sources maintain a constant current through them. These sources are fundamental building blocks in circuit design, enabling the supply of energy to power electronic devices and systems.