31_SI_UNITS

• Building Services
• Further Education (Key Stage 5)

What are you going to learn?

In this lesson you're going to learn about SI units

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What are the SI 

Units

Basic SI units

The Electrical SI

Units

Basic SI units, multiples & unit conversion

SI units

Over the years it has become increasingly obvious that when trying to understand one another it is better that a common form of expression is adopted, particularly when engineers, scientists etc. need to communicate. If there was no common understanding a large number of differing standard forms would be adopted making conversion of units difficult.

Defintion of SI Units

^{This system of common identification of units is called Systeme Internationale d’unities, shortened to SI units.}

Number of SI Units

There are seven fundamental units and of these it is only necessary for us to remember five of them.

SI Units

Five Basic SI Units

1. Length  (m)
2. Mass      (Kg)
3. Time      (sec)
4. Current (Amp)
5. Temperature (Kelvin)

The seven SI base units

1. Length - meter (m)
2. Time - second (s)
3. Amount of substance - mole (mole)
4. Electric current - ampere (A)
5. Temperature - kelvin (K)
6. Luminous intensity - candela (cd)
7. Mass - kilogram (kg)

SI Basic Units

Size of Units

5000 watts is Equivalent To

Text

1. 5KW
2. 5MW
3. 5TW
4. 5GW

2500000VA

1. 25KVA
2. 2.5GVA
3. 0.25GVA
4. 2.5MVA

Conversion Table

7 x 1000

1. 7000
2. 70 000