Electrical Installation Mathematics

2 - Mathematic Principles

Ohms Law

3 - Resistors in Series

Volts = V

Ohms = R

Amperes = I

Piv Triangle

Volts = V

Watts = P

Amperes = I

Resistors in series

4 - Resistors in Parallel

resistors in parallel common denominator 1/RT = (1/R1 + 1/R2 + 1/R3)

Find the common denominator for all the resistors, add them together and inverse the fraction

Resistors in parallel use Reciprocals

Turning a number into a fraction 5 = 1/5

P = I² x R

P / R = I²

Formula wheel VIPR

Sine waves

RMS 0.707 x peak value

0.646 x Avg

14 - Basic Mechanics

Gravity = 9.81m/s2

Add them together

1 litre of Water Weighs 1kg 1L of water is 1kg

Mass(kg) x 9.81 = Force

Cable Selection

Energy Is the capacity for doing work. It may exist in in potential, kinetic, thermal, electrical, chemical, nuclear forms. The unit of energy is the newton metre or Joule

Force x Distance = Energy

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16 Levers

less than

more than

Cable selection update )

Key seperate

Ib Design current of circuit

IZ current carrying capacity of cable for particular insallation conditions

tabulated current carrying capacity of a cable

In rated protective device