What is an Ampere?


What is ampere in electricity? First, let’s answer the question, “What is a current?” Current is the measure of the rate at which electrons “flow” in a circuit. Ampere is a basic unit that measures current, and is frequently shortened to “Amp.” It’s a measure of the amount of electric charge that passes a point in a circuit per unit time with 6.241 × 1018 electrons, or one coulomb per second comprising one ampere. Ampere for electric current is one of the seven SI base units, which include:

  • Ampere for electric current
  • Second for time
  • Metre for length
  • Kilogram for mass
  • Kelvin for temperature
  • Mole for amount of substance
  • Candela for luminous intensity

What is Ampacity?

Measured in amperes, ampacity refers to the maximum current-carrying capacity of a conductor, such as a cable, without surpassing its maximum operating temperature. How well a device can dissipate heat greatly impacts its ampacity. Current-carrying capacity is especially important when choosing a cable. Heating is the effect of current flow resistance, and the size of the conductor, the insulation material, and external factors, play a large role in current-carrying capacity and heat resistance.

Generally, the larger the conductor, the lower the current flow resistance. A larger conductor also means a greater current-carrying capacity. When the current-carrying capacity of the conductor (or a cable in this example) is high, the temperature resistance of the insulating material also needs to be high to accommodate. Insulation material with a with 190 degree F temperature rating will have a higher current-carrying capacity than insulation material rated at 150 degrees F.

How to Calculate Watt to Ampere

You can use Watt’s Law to convert watts to amps. This formula states that I = P / E. I, or current measured in amps, equals P (power measured in watts) divided by E (voltage measured in volts). If you wanted to find the amperage of 1,200 watts at 120 volts, you would use the following formula:

  • current = power / voltage
  • current = 1,200W / 120V
  • current = 10A

If you know the resistance of the circuit, you can convert watts to amps with the following formula:

  • amps = √(watts × ohms)

Learn More with Gateway Cable Company!

If you’ve ever wondered, “What exactly is an ampere?”, we hope the above information has answered your question. If you’d like to know more about amperes and the role they play in electrical equipment, or if you want to know more about electrical insulation materials like polycarbonate, or you’re looking to purchase cables with a high current-carrying capacity, Gateway Cable Company can help. Contact us or request a quote on any of our products online!