Basic Electrical Ohms Law Formula
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Summary: This article shows you how the Ohms Law Formula is used for determining electrical loads as it pertains to Watts, Volts and Amps. Ohms Law is very helpful to help us understand sizing electrical circuits for the home electrical system. |
Basic Ohms Law Formula for Electrical Wiring Calculations |
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| The Ohm's Law Calculations for Electrical Using the Ohm's Law is a way to determine information needed to understand how to design electrical circuits. This formula works with three main variables and depending on what is known can produce a missing factor which is needed to determine the circuit size. The Ohm's Law is also used when designing appliances and building electrical equipment and devices. |
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Example: A Microwave Oven circuit |
| Device ________________ Volts __________________ Amps _________________ Quantity _______________ Circuit Size Amps ________ Wire Size _______________ [ see wire size chart ] |
Help with understanding Electrical Appliance Labels
This Microwave Oven requires a 1500 Watt Circuit of 120 Volts.
1500 /120 Volts = 12.5 Amps.
A good rule is to never load a circuit past 80% of the circuit capacity. An 80% load on a 15 Amp circuit would be 1200 Watts so this would require a circuit one size larger.
Installing a circuit for this microwave oven would require a 20 Amp / 120 Volt Circuit.
In kitchens it is common practice that if a microwave oven will be installed at a given location, such as Hood-Fan Microwave Ovens, that a Dedicated 20 Amp Circuit is always installed.
