Question

which of the following is not a fundamental unit .1 )cm 2)kg 3)centigrade 4) volt​

Answer 1

Volt is not a ‘fundamental unit’, it is a derived unit.

Answer - Volt (Option 4)

Explanation:

• Volt is not a ‘fundamental unit’, it is a derived unit.
• A ‘derived unit’ is a unit derived from the basic fundamental units of the SI system like meter, kilogram, second, ampere, Kelvin or centigrade, mole, and candela.
• A volt is a derived unit which is used to measure the potential difference or the “energy per unit charge”.
• “one volt is one joule of ‘energy per coulomb’ of charge”.
• In SI system, volt is represented basically as 1 V = $\mathrm{kg} \mathrm{m}^{2} \mathrm{s}^{-3} \mathrm{A}^{-1}.$
• So a volt is derived from the fundamental units – “kg, m, s, and A”.

Answer 2

Volt (4) is not an SI unit.

Explanation:

• The International system of units (SI) has selected 7 basic units in the field of study. These are called the basic or fundamental units.

• Since they are not derived from any other units. For example metre for length is a basic fundamental SI unit . All other units that we use for calculations of length in SI are derived, such as millimetre, it is a derived form of the unit metre.

• Similarly all the units that we use across the world in SI system are derived using these basic 7 units those are namely,

1. Length - metre (m)
2. Time - seconds (s)
3. mass - kilogram (kg)
4. Current - ampere (A)
5. amount of substance - mole (mole)
6. Temperature - kelvin (K)
7. Luminous intensity - candela (cd)

• Hence, of the given options, volt (4) is not an SI unit as it does not find its name in the above list, and also because it is a derived unit.