What is Current? Electricity fundamentals

Understanding current in electrical circuits

What is current amps

Electricity is the flow of electrons from one atom to another. When we talk about current with regards to electricity, we are referring to the amount of electrons flowing past a single point in a circuit.  Imagine it like measuring how drops of water are flowing past you in a river.
You might want to learn a little about what electricity is first before proceeding, we covered that here.

Because electrons are so small, vast numbers of them can flow through even the smallest circuit. Just like a vast number of water droplets can flow past you in a small stream.

To be able to quantify the flow of electrons in a circuit, scientist derived some units of measurement to group millions and millions of electrons together. As much as it wouldn’t be practical to measure the flow of drops in a river, it isn’t practice to measure the flow of electrons in a circuit. So units of measurement were created to measure this.

The SI unit of measurement for current is known as the Ampere, or Amp for short. The symbol A is used to represent this value. See Figure 1 below.

Amp meter
Figure 1: ACB Amp reading

This is an Amp reading from an ACB. It reads that on cable 1, there are 346Amps flowing at that specific moment in time. That’s a lot of electrons! I’ll explain why below.

So I mentioned that electron are grouped together, these groups are called Coulombs. How many electrons are in a Coulomb?

1 Coulomb = ~6,242,000,000,000,000,000 electrons! (6.242*10^18)

1 Amp = 1 Coulomb

So in the example where 346Amps were flowing in that cable, how many electrons were flowing?

346A = 346 Coulombs
346*6.242*10^18 = 2.16*10^21
or 2,162,500,000,000,000,000,000 Electrons. Now do you see why we use the unit of Amps.

You may also come across a current rating in mA which is known as a milliampere or milliamp for short. A milliamp is one one-thousandth of an ampere.

To convert milliamps to Amps simply divide by 1,000.
e.g. 400mA = 400mA/1000 = 0.4A
To convert Amps to milliamps simply multiply by 1,000.
e.g. 0.4A = 0.4A*1,000 = 400mA


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