Railway Science (Physics-Electric Current and its Effects) (Part-V)

(Unit - Ohm). Rheostat - The variable resistor is a type of resistor whose electrical resistance value can be adjusted as per our demand. Working principle - Ohm’s Law. Factor affecting Resistance - Material's conductivity, Length, Cross-sectional area, and Temperature. Other Physical Quantities - Temperature (Kelvin), Electric Current (Ampere), Potential Difference (Voltage).

Filling a bulb with an inert gas slows down tungsten filament evaporation compared to operating in a vacuum, enabling higher temperatures, greater efficacy, and less reduction in filament life. The first commercial electric bulb was first invented by Thomas Alva Edison in 1879.

Electric current is the flow of electric charge. In most electrical circuits, this charge is carried by electrons moving through a conductor. In the International System of Units (SI), electric current is expressed in units of ampere, which is equivalent to one coulomb per second.

Electric iron - The electrical energy changes into heat energy. Torch - Chemical energy stored in cells is converted into electrical energy. Television - Electrical energy is converted into light energy.

Electromagnetic force: This force arises from the interaction between electrically charged particles. It manifests as both electrical and magnetic forces, responsible for phenomena like electric currents, magnetism, and light.

It is a device used to measure the potential difference between two points in a circuit. It is connected in parallel to the circuit. Some symbols: For unconnected wire crossing:

Materials that do not allow electricity to pass through them are called electrical insulators. Insulators oppose electric current and so they are used as a protection from the dangerous effects of electricity. Examples- Plastics, ebonite, paper, cotton, Bakelite, dry air, rubber. Materials that allow electricity to pass through them are called Conductors. Example - Silver, Copper, Gold, Iron, Aluminium.

Energy Transformation Devices : Dynamo - Mechanical energy into electrical energy. Microphone - Sound energy into electrical energy. Loudspeaker - Electrical energy into sound energy. Electric Bulb - Electrical energy into light and heat energy.

A fuse is a safety device designed to interrupt current flow when it exceeds a specific limit, protecting electrical circuits from damage caused by overheating. It is made up of an alloy of lead, tin, or zinc.

Types of electrical (circuit) connections: Series Connection: Components are connected end-to-end, providing only one path for current flow. Parallel Connection: Components are connected across common points, providing multiple paths for current flow.