Electric Charge, Current, Circuits, and Power Generation
Fundamentals of Electricity
Electric Charge: Substances are made of atoms, and atoms contain electrons, protons, and neutrons, which possess electric charge.
Electric Current: This consists of the movement of electric charges through a conducting material, such as copper or aluminum.
Generating Electric Current
Generator: A device that creates and maintains the voltage needed to produce and sustain an electric current.
Electrical Circuits: These are formed by a generator and several interconnected elements connected by cables.
Ways to Generate Current
Electric current can be generated through various methods:
- Chemical reactions (e.g., batteries)
- Pressure (piezoelectricity)
- Movement (e.g., generators, dynamos)
- Light (photovoltaics)
Key Electrical Concepts
Voltage (Supply): The electrical potential difference or energy needed to drive the circulation of charge (current).
Intensity (Current): The amount of electric charge passing through a section of a conductor in a specific time. It represents the speed of charge flow. Current depends directly on voltage and inversely on resistance.
Electrical Resistance: The degree of opposition a material offers to the passage of electric current.
Ohm’s Law and Power Formulas
Ohm’s Law describes the relationship between voltage (V), current (I), and resistance (R):
- V = I * R (Voltage = Current × Resistance)
- I = V / R (Current = Voltage / Resistance)
- R = V / I (Resistance = Voltage / Current)
Electric Power (P): The rate at which electrical energy is transferred.
- P = V * I (Power = Voltage × Current)
Electrical Energy (E): The total power consumed over a period of time (t).
- E = P * t (Energy = Power × Time)
- E = (V * I) * t
AC vs. DC and Induction
Electric Induction: When a conductor is moved relative to a magnet (or vice versa), an electric current is produced within the conductor.
Alternating Current (AC): Current where the direction changes periodically. It has no fixed polarity. AC is produced by alternators and is commonly used in homes and factories.
Direct Current (DC): Current that maintains its direction and polarity. It is obtained from sources like batteries and dynamos.
Dynamo: A machine used to generate continuous (direct) electric current.
Electric Motors Explained
Components of an Electric Motor
- Stator: The fixed part of the motor, connected to the housing.
- Rotor: The rotating part of the motor.
- Inductor: The part that creates the magnetic field (often the stator).
- Induced Part (Armature): Formed by one or more coils, where the current interacts with the magnetic field (often the rotor).
- Collector (Commutator): Responsible for carrying current to the rotating coil in DC motors.
- Brushes: Transmit power to the collector/commutator.
Turbines and Cogeneration
Turbine: A set of blades attached to a shaft. A fluid (like water, steam, or air) exerts pressure on the blades, causing the shaft to rotate.
Cogeneration: A procedure by which electric power and useful thermal energy (heat) are obtained simultaneously from the same energy source.
Types of Power Plants
Nuclear Power Plants
The energy required to move the alternator rotor is obtained from steam. This steam is generated by boiling water using heat from a nuclear reactor.
Hydropower Plants
The turbine is driven by the force of falling water stored in a reservoir, turning the generator.
Mid-Temperature Solar Power
Solar radiation hits collectors (mirrors) that focus it onto a small receiver surface. This achieves high temperatures, and the stored heat produces pressurized steam to drive a turbine.
High-Temperature Solar Power (Solar Towers)
Solar radiation hits a large surface covered with mirrors (heliostats). These concentrate the radiation onto a central collector, often on a tower, where heat drives a turbine.
Wind Power
Wind turbines have blades turned by the wind. This rotation moves a shaft connected to an electric generator, producing power.
Transformers and the Grid
Transformers: Devices used to increase or decrease the voltage in an alternating current (AC) electric circuit. They consist of two coils (primary and secondary) wound around an iron core.
Electrical Grid: The network that transmits electricity from power plants to homes and businesses through interconnected transmission and distribution lines.