Units and Measurement

4      1 kWh = 1 kilowatt per hour

4   1 volt is equal to the difference of electric potential between two points on a conducting wire carrying a constant current of one ampere when the power dissipated between the points is one watt. Clearly it cannot be a basic unit

4    To measure the fundamental physical quantities Length, Mass and time we have three systems of units, they are (i) C.G.S System (ii)F.P.S System and (iii)M.K.S System. In all these three systems only three physical quantities length, mass and time are considered to be fundamental quantities.But, in systems International (S.I) system there are seven fundamental physical quantities. Which are (i) Length( ii) Mass( iii) Time (iv) Electric current (v) Thermo dynamic temperature (vi) Luminous intensity( vii) Quantity of substance.

3   Inertia is the resistance of mass

4    The ratio of the magnetization of a material to the magnetic field strength is called magnetic susceptibility; it is a tensor when these two quantities are not parallel; otherwise it is a simple number. Poisson ratio is a ratio i.e. a number ( Number is a unit less thing)

1    dyne is the CGS unit of force, Definition: it is the force which accelerates a mass of one gram at the rate of one centimetre per second .

3      the CGS unit of magnetic flux density is gauss This exerts a force of 0.1 dyne per ampere on a current-carrying conductor placed in the field.

3   The CGS unit of heat energy is cal. The amount of heat required at a pressure of one atmosphere to raise the temperature of one gram of water by one degree Celsius.

1        The newton, is the force which accelerates a mass of one kilogram at the rate of one meter per second . The ratio between a CGS unit and the corresponding MKS unit is usually a power of 10. A newton accelerates a mass 1000 times greater than a dyne does, and it does so at a rate 100 times greater, so there are 100 000 = 105 dynes in a newton.

2   The SI unit of magnetic flux is weber . Flux is the rate (per unit of time) at which something crosses a surface perpendicular to the flow. If the something is a magnetic field, then the magnetic flux across a perpendicular surface is the product of the magnetic flux density.

3   There are seven base SI units (for mass, length, time, electric current, temperature, luminous intensity, and amount of substance) from which the other units may be derived.

A light-year is a unit of length used by astronomers to measure interstellar distance (the distance between stars). A light-year is defined as the distance that light will travel in a year.

The decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, most commonly sound pressure level.

The pascal (symbol: Pa) is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre.

Basic units (or fundamental units) are the units of physical quantities that cannot be derived from other physical quantities.