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

A machine that converts mechanical energy into electrical energy. Electromagnetic induction - Production of an electromotive force across an electrical conductor in a changing magnetic field. Cyclotron - A device used to accelerate charged particles or ions to very high energies.

Solenoid: A coil of many circular turns of insulated copper wire wrapped closely in a cylinder's shape. Magnetic field of a solenoid carrying current is similar to a bar magnet as it also has the poles on either side and field lines (magnetic) are curved outside and straight inside the solenoid. An image will reflect through a line, known as the line of reflection.

A positive charge occurs when an atom has more protons than electrons. Dielectric - It is a substance that possesses insulating properties and has the ability to transmit electric force without conduction. Magnet - An object which is capable of producing a magnetic field and attracting unlike poles and repelling like poles. First, create a magnet by William Gilbert. Negative charges - When an object has more electrons than protons is called a negative charge.

The work done per unit charge from one point to another. V = W/Q.  Here, W = Work, Q =  Electric charge. Quantities and their units: Potential difference - Volt (V), Work - Joule (J), Charge - Coulomb (C), Resistance - Ohm (Ω).

Converts electrical energy into heat which is used to cook food. Electric motor - The device in which electrical energy is converted into mechanical energy. Transformer - A passive electrical device that transfers electrical energy from one circuit to another through the process of electromagnetic induction. Generator - Converts mechanical energy into electrical energy.

Resistance - It is the measure of the opposition to the flow of current in an electrical circuit. SI Unit - ohms, denoted by omega (Ω). The relationship between resistance (R), length (l), cross-sectional area (A), resistivity (ρ), and temperature (T) is given by the following formula: R = ρ × 𝑙/𝐴 . Temperature - It is directly proportional to resistance. Resistivity - The resistance offered by the material per unit length for a unit cross-section.

A conductor is a substance or material that allows electricity to flow through it. Examples - Silver, Steel, Gold, and Aluminium. Resistance (R) = ⍴(L/A). ⍴ (rho) is resistivity, L is the length and A is Area of Cross section. Resistivity is the property of a material to resist the flow of electric current. Insulator: Materials that do not permit heat and electricity to pass through it. Examples - Plastics, Styrofoam, paper, rubber, glass.

The electrons flow from the negatively charged plate through the wire to the positively charged plate of the cell. Conventionally the direction of the current is taken as opposite to the direction of the flow of electrons i.e., from the positive to the negative terminal.

A strong metal with a high melting point such as tungsten (melting point 3380°C) is used for making bulb filaments. The filament should be thermally isolated as much as possible, using insulating support, etc. The bulbs are usually filled with chemically inactive nitrogen and argon gasses to prolong the life of filament.

A sudden flow of a very large current due to direct contact of a live wire and a neutral wire. Fuse - A device used in an electrical circuit for protecting electrical devices against overloads and short circuit. Overloading - When current flows in a circuit, it becomes more than the capacity of components in the circuit to resist the current.