Rectifier is an electrical device that converts alternating current (AC) into direct current (DC). It is commonly used in power supplies, battery charging systems, and DC motor drives. Rectifiers can be half-wave, full-wave, or bridge rectifiers, depending on their design and efficiency. They use diodes or thyristors to allow current to flow in only one direction. Some rectifiers also include filters to smooth the DC output. They are essential in electronics, industrial automation, and renewable energy systems, where DC power is required.

Relays are electrically operated switches used to control circuits by opening or closing contacts in response to an electrical signal. They are commonly used in power systems, automation, and safety applications. Types of relays include: - Electromechanical Relays (EMR): Use a physical moving part (armature) to switch contacts. - Solid-State Relays (SSR): Use semiconductor components for faster, silent operation. - Protective Relays: Detect faults like overcurrent or voltage fluctuations in power grids. Relays help in circuit isolation, automation, and electrical protection.

Resistance is the property of a material that opposes the flow of electric current in a circuit. It is measured in ohms (Ω) and follows Ohm’s Law, which states that resistance is equal to voltage divided by current (R = V/I). Higher resistance reduces current flow, while lower resistance allows more current to pass. Resistance depends on material type, temperature, and conductor size. Materials like copper and aluminum have low resistance, making them good conductors, while rubber and plastic have high resistance and are used as insulators.

RTU (Remote Terminal Unit) is an industrial device used in SCADA (Supervisory Control and Data Acquisition) systems to monitor and control remote electrical or mechanical equipment. It collects data from sensors, meters, and switches, processes it, and transmits it to a central control system via wired or wireless communication. RTUs are widely used in power distribution, oil and gas, water treatment, and industrial automation. Unlike PLCs, RTUs are designed for harsh environments, have built-in communication capabilities, and often operate on low power for remote locations.