To determine the amperage demand, divide the watts of a specific electrical item by the entire number of volts accessible from the electric outlet. Amperes, or amps, are used to quantify the amount of current flowing through the wire. Voltage, which is measured in volts, is the equivalent of available electricity at the power source. Wires with different numbers of wires inside them have different amp ratings. The more conductors there are in a cable, the greater its capacity for carrying electricity.
The term "amperage rating" refers to the maximum continuous current that can be carried by a conductor of a given size without failing. The term "amps" has become standard terminology for describing the current-carrying capacity of wires and cables. The United States government requires that all wiring within the country be listed as to type and ampacity. The two types are copper and aluminum. Aluminum wiring was originally used because it was lighter than copper wiring of equal size; however, today it is only used in very small quantities because it is more prone to corrosion. Copper is used almost exclusively for large wires because they can carry more current than smaller wires of the same material. The current flowing through a conductor causes heat to be generated, so the higher the amperage, the more likely it is that something will fail. The average household current is around 120 volts, so the maximum amperage that can be used for household wiring is 12 amps.
Amperage Calculation The watts divided by the volts is a simple formula for computing amps. So, for example, if the wattage of the lighting fixture is 60 and the volts are 12, divide 60 by 12 to get five, which is the amps. Most appliances that use electricity such as lamps, heaters, and air conditioners are rated by their wattage so you would use this calculation method for determining their amp load.
However, many appliances that use electricity such as washers, dryers, and dishwashers are not rated by their amp load but rather by their continuous current capacity. For these appliances, you need another method; we will discuss those methods below under the sections on Calculating Loads for Specific Appliances.
Finally, some appliances have both types of loading: they can be rated in amps or more commonly in continuous current capacity. Examples include floor lamps and table lamps. If you are unsure whether an appliance is rated in amps or continuous current capacity, look on the manufacturer's website or call them directly to make sure.
For example, a floor lamp that is only rated at 20 watts but that uses 15 watts of power when lit for 4 hours per day for one month of summer time usage from 6am to 2am is a low-amp load device.
The method for calculating the number of amps drawn is as follows: [Total Wattage of Devices Plugged Into the Circuit] / [Voltage of the Circuit] = [Amps Drawn from the Circuit]. Assume you're using a single outlet in your living room to power a 150-watt light and a 1,500-watt space heater. The voltage in the circuit is 120 volts, so the amp draw for the light and the heater combined is 30 amps or less.
The total wattage of the lights and heater is 150 watts, so its wattage in parallel should be 300 watts. Since all appliances have different power ratings, it's best to calculate the amp draw for each device and add them together. In this case, it's easy because there's only one light and one heater, so their combined amp draw is 30 amps or less. Your electric company can tell you what percentage of power is used by each appliance, but for now, just assume that 20 percent of 300 watts is 60 watts. That means you need an outlet that can handle at least 80 watts in parallel if you want to power both devices at once.
You should also know that some countries have electrical code requirements for minimum distances between outlets. These codes usually require certain amounts of spacing between power sources of equal strength (such as two wall sockets or one extension cord plugged into both). Make sure you follow any such requirements when placing your outlets.
Watts divided by Volts is the formula for Amps. To utilize the chart, place your finger on the A and apply the remaining chart calculation of W divided by V. Using the data from our sample panel, 60 watts divided by 12 volts equals 5 amps.
Calculating voltage from amps and power: Power (P) in watts divided by current (I) in amps equals voltage (V) in volts. As a result, the equation will be Voltage = Power/Current. If you know one of these quantities, you can easily find the other two.
For example, if you know that the power is 1,000 watts and that the current is 10 amps, then the voltage must be 100 volts. Or if you know that the current is 80 amperes and that the resistance is 4 ohms, then the power is 400 watts. The voltage will be 400 divided by 0.04, which equals 100 volts.
Voltage is measured in volts, and it's the force between atoms or molecules that creates electricity that determines how much voltage is available at any given time. Current is the flow of electrons through a conductor such as a copper wire; it is usually expressed in amperes (amps). Power is the amount of energy transferred in one unit of time, and it is the product of voltage and current; thus, power is equal to voltage times current. Energy comes in many different forms, but only electrical energy is used by humans so it is important to understand its relationship to other forms of energy.
Knowing these three concepts will help you understand what is going on when you use electricity in your home.