Amps, volts and watts in electricity – the relation

Amps, volts and watts are popular units in the field of electricity. You may have seen the voltage rating and power rating on electronic and electrical devices. These imply the amount of power the device will consume and at what maximum volts the device should be operated. In this article, we’re going to compare these quantities and units and will discuss how they are related to each other.

Contents of this article:

  1. Comparison between amps, volts and watts.
  2. What is the relation between amps, volts and watts?
  3. How to find wattage if amps and volts are given?

Comparison between amps, volts and watts

Amps, volts and watts are the units of three different physical quantities of an electrical circuit – current, voltage and power. They are measured to identify whether the circuit is capable to run a device or not. Here is a short discussion on these units.

What are amps?

The full form of amps is amperes. The electric current through a circuit or device is measured in the unit of Ampere or amp. It gives an idea of the amount of electric charge in coulombs that flows through the circuit or device. The ammeter measures the amps in a circuit. In simple words, one-ampere current is defined as the amount of electric charge flows through a cross-section per second.

What are volts?

Volt is the SI unit of the electric potential difference or voltage drop between two points in a circuit or across a device connected in a circuit. A voltmeter can measure the volts of a battery or across a device.

Volt is the unit of voltage or potential difference. If the work done in moving a 1-coulomb positive charge from one point to another is 1 Joule, then the electric voltage difference between those two points is said to be 1 volt.

What is one Watt?

Watt is the SI unit of electric power which refers to the amount of electrical energy consumed by a device per unit second. From the power rating of a device, we can determine how many amps it will draw. Watts gives the measure of the power rating or wattage of a device.

Watts is the unit of Wattage or electric power. If a device consumes 1 Joule amount of energy per second, then its wattage or power is 1 Watt. Here is how many amps are required for a 1500 Watts heater.

Comparison Table

Here are some key differences between amps, volts and watts in a tabular form –

SL no.AmpsVoltsWatts
1Ampere is the unit of amperage.Volt is the unit of Voltage.Watt is the unit of Wattage.
2It’s the amount of electric charge that flows per second.It’s the work done to move +1C charge.It’s the consumption of energy per second.
3Ammeters measure amps.Voltmeters measure volts.Power meters measure watts.
4It’s a fundamental physical quantity.It’s not a fundamental physical quantity.It’s also not a fundamental physical quantity.
Differences between amp, volt and watt

What is the relation between amps, volts and watts?

Voltage, amperage and wattage of a circuit are related to each other. Their units also have a relation between them. If V amount of voltage can pass I amount of electric current through a device, then

The electric power consumed, \small \color{Blue} P = IV…….(1)

That means the Electric Wattage = Amperage × Voltage.

Hence the relation between their units i.e. amps, volts and watts is Watts = Amps × Volts………(2)

How to find amps if wattage and volts are given?

Let’s solve a numerical problem on voltage, amperage and wattage. Consider a problem first!

Numerical problem:

If the power rating of a device is 1500 Watts, then how many amps will it draw if it is connected to 240 volts?


The power of the device is P = 1500 Watts and the voltage across it is V = 240 volts. Then from equation-(1) we get,

\small \color{Blue} P = IV

or, \color{Blue} I = \frac{P}{V}

or, \color{Blue} I = \frac{1500}{240} = 6.25

Thus the device will draw 6.25 amps of electricity to operate.

This is all from this article on amps, volts and watts in electricity. These units are used to express the measures of amperage, voltage and wattage. Hope you get your answer.

Thank you!

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