Units and Measurement

The SI unit of time is the second (s). Metre is for length, ampere for electric current, and candela for luminous intensity. The second is defined based on the radiation frequency of the cesium-133 atom.

Mg is the chemical symbol for Magnesium, a metallic element with atomic number 12. It is an alkaline earth metal in Group 2 of the periodic table. Manganese is Mn, milligrams is a unit abbreviation (mg in lowercase), and MW stands for megawatts for power.

The SI unit of magnetic flux is Weber (Wb). Magnetic flux (Φ) is the total magnetic field passing through an area. Tesla is the unit of magnetic flux density (B field), not flux. Weber per square meter would be magnetic flux density, not flux. Gauss is a non-SI unit for magnetic flux density.

A light year is the distance light travels in one vacuum year (about 9.46 trillion kilometers). Despite containing the word 'year', it measures astronomical distance (length), not time or speed.

Ohms is correctly identified as the unit of electrical resistance, named after Georg Ohm who formulated Ohm's Law (V=IR). Newton measures force, Mhos (now called Siemens) measures conductance (the inverse of resistance), and Cadila is not a physical unit. Resistance is fundamental to electrical circuits and determines how much a material opposes current flow.

The Ampere (A) is the standard International System of Units (SI) unit for electric current. Ohm is the unit for resistance, Farad for capacitance, and Mho (an older term for Siemens) for conductance.

An ammeter is an instrument used to measure electric current in amperes. A cubit, parsec, and angstrom are all units used to measure length or distance at various scales (human, astronomical, and atomic).

One unit of electricity is defined as one kilowatt-hour (kWh), which means using 1 kilowatt (1000 watts) of power for 1 hour. This is the standard unit for billing residential electricity consumption worldwide.

Joule is the SI unit of energy or work. It measures the amount of energy transferred when a force of one newton acts over a distance of one meter.

One joule equals 10^7 ergs because 1 J = 1 kg·m^2/s^2 and 1 erg = 1 g·cm^2/s^2, so 1 J = (1000 g) × (100 cm)^2/s^2 = 10^7 erg.

The ampere is the SI base unit for electric current, measuring the flow of electric charge. Ohm is the unit of electrical resistance, and watt is the unit of power.

The joule is the unit of energy in the MKS (meter-kilogram-second) system, which is the basis of the modern SI system. The erg is the energy unit in the CGS system, while volt measures potential difference and ohm measures resistance.

The charge-to-mass ratio (e/m) of an electron has units of coulombs per kilogram (C/kg) since it is obtained by dividing the charge in coulombs by the mass in kilograms. J.J. Thomson measured this ratio to be approximately 1.76 × 10^11 C/kg. This specific ratio helped identify the electron as a fundamental particle. Option B correctly represents the unit as C/kg. Options A and D are incorrect units, while e/m is not dimensionless.