Railway Science (Physics-Units and Measurements)

Kilowatt - hour : It is the unit of energy and is equal to the energy consumed in the circuit at the rate of 1 kilowatt for 1 hour. Electrical energy: The energy that is derived from the flow of electric charge is called electrical energy. The SI unit of electrical energy is Joule. Electric Power: The rate at which electrical energy is consumed in a circuit is called electric power. The SI unit is the watt.

Magnification is the ratio of the height of an image to the height of an object,
m = ℎᵢ/ℎₒ . Magnification in convex lenses is positive for virtual images and negative for real images and in concave lenses it is always positive, but less than 1.

A calorie is a unit of measure of energy. SI unit of energy is the same as that of work, which is joule (J). SI unit : Resistance - Ohm (Ω), Electric current - Ampere (A), Force - Newton (N), Temperature - Kelvin (K), Amount of Substance - Mole (mol), Luminous Intensity - Candela (Cd), Power - Watt (W), Pressure - Pascal (Pa).

Ohm - unit of electrical resistance. Coulomb - unit of electrical charge. Watt - unit of electrical power. Newton - unit of mechanical force. A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity.

meter - It was originally defined in 1791 as one ten-millionth of the distance from the equator to the North Pole along a great circle. SI base units - kelvin (thermodynamic temperature), mole (amount of substance), candela (luminous intensity). Other facts - 1 Inch = 2.54 cm. 1 Foot = 0.3048 m. 1 Mile = 1609.34 m.

It is defined as 6.022 × 10²³ particles. Units of some physical quantities : Tesla - Magnetic Flux Density. Lux - illuminance.

Ammeter - An instrument for measuring either direct or alternating current (SI Unit - Amperes). Fluxmeter - Measure the magnetic flux of a permanent magnet. Bolometer - Measuring radiant heat by means of a material having a temperature-dependent electrical resistance.

Scientific instruments: Anemometer - Wind's speed. Dynamometer - Computes power, torque, and force. Electroscope - Detects the presence of an electric charge. Rectifier - Used for the conversion of AC into DC.

A voltmeter - Measuring electric potential difference between two points in an electric circuit. Rheostat - Variable resistor which is used to control current.

It is a useful way of examining many of the body's internal organs. Reverberation is the accumulation of soundwaves in a space. A repeated sound that is caused by the reflection of the sound waves from the surface is called Echo. SONAR (Sound Navigation and Ranging) is a technology that uses acoustical waves to sense the location of objects in the ocean.