Adafruit is celebrating National Week of Making with a sale! Get up to 15% off select items at No code necessary.

January 2, 2011 AT 1:56 pm

Please welcome Jeri Ellsworth to Adafruit videos! Ampere – A to Z of Electronics

2011 is going to be an amazing year for people who love electronics, TONS OF STUFF AHEAD FROM ADAFRUIT! And we’re kicking it off with a new video series with one of our friends! Please welcome Jeri Ellsworth to Adafruit videos! The first video is “Ampere – A to Z of Electronics” we will have 25 more videos, one about every week, here’s the first one – enjoy! Ampere is a unit of measurement for current and was named after André-Marie Ampère.

The ampere, or amp for short, is a common measurement used in electronics, and is named after the French scientist Andre-Marie Ampere. He never went to school as a young boy, but had a very strong desire to learn, and was said to have read the dictionary in alphabetical order. At the age of 13, he submitted his first mathematical paper, but it was not deemed worthy of publication. This rejection helped him realize he needed to be more diligent about his studies.

His life was full of tragedy, the first being when his father was executed during the French Revolution. This sent him into an 18 month depression, in which he gave up his studies. During this period he met his future wife, and decided to take a job tutoring math to prove he could earn a living. This eventually led to a position as a professor. He later took another job in a distant city away from his wife, who had become ill.

I have science to do, au revoir.

Her health continued to decline, and she eventually passed away a year later. This troubled Ampere for the rest of his life.

I am Napoleon.

Although the Napoleonic Wars were being waged at this point–

Out of my way.

–Ampere was still allowed to collaborate with scientists from enemy countries. One week after hearing of Hans Christian Oersted’s discovery that a magnetized needle could be influenced by an electric current flowing, Ampere demonstrated more complete explanations of the effect, by showing that two wires would be attracted to one another when the current flowed in the same direction. Or repelled when the current flowed in opposite directions.

Current is the flow of charge. It can be through wires, air, liquid, or even a vacuum. It wasn’t entirely clear to the early pioneers of electronics, what was actually flowing through wires, positive charge or negative charge. They made a guess that it was positive, and they didn’t get it right. We now know that protons are held by strong nuclear forces, and it’s actually electrons moving.

For day to day electronics you can think about the charge flowing in either direction, the mathematics will always work out for you. Mostly you’ll be working with conventional current flow, positive to negative, although that’s not what is happening.

Current is measured by the number of electrons that pass by a point in a given time. Amperage, indicated by the letter I, is the amount of charge per second, and the charge is in coulombs. One coulomb per second is one amp. If you’re curious, this is how many electrons one coulomb is. That’s a whole lot of electrons.

For many circuits that you design, you’ll need to know how much current is flowing, or how to measure that current. For instance, many components in wires have a maximum current rating. We’re going to use the simple circuit with resistor and a battery to do some Ohm’s Law calculations. Ohm’s Law is current equals voltage divided by resistance.

Some things to keep in mind is that current is proportional to voltage. The more the voltage, the more the current. Resistance has the opposite effect– more resistance, the less current. If we’re looking for one amp of current flow in our circuit, and we have a one volt battery, then our resistor needs to be a one ohm resistor. It’s pretty simple math, one volt divided by one ohm equals one amp. If we double the voltage of the battery, it’s easy to see that the current flow will be doubled in our circuit.

OK, say we want to measure some current. We can put a resistor in series with our circuit, and measure the voltage drop across the resistor, and use Ohm’s Law to determine the current flowing through our circuit. There are also electromechanical means for measuring amperage. The ammeter is very similar to the early experiments with the magnetized needle. Many ammeters are constructed with a permanent magnet, and a coil wire wrapped around the magnet. When current flows through the coil, the meter needle is deflected in relation to the amount of current.

There are many ways to measure current, so I’m going to cut it short here. I did want to mention that the early pioneers of electromagnetism really laid the foundation for many devices that we use every day.

So I hope you like the new video series, A to Z of Electronics. It was sponsored by Adafruit Industries, be sure to go check out their stuff. They’ve got hundreds of hobby project kits, and educational stuff. They even have test equipment, so you can test amperage. If you like it, be sure let them know. And if you don’t like it, well, just keep that between us, right? And as always, you can reach me at [email protected]

And it’s named after the French scientist Andre Me me me Me me me me.

Check out all the Circuit Playground Episodes! Our new kid’s show and subscribe!

Have an amazing project to share? Join the SHOW-AND-TELL every Wednesday night at 7:30pm ET on Google+ Hangouts.

Join us every Wednesday night at 8pm ET for Ask an Engineer!

Learn resistor values with Mho’s Resistance or get the best electronics calculator for engineers “Circuit Playground”Adafruit’s Apps!

Maker Business — Transforming Today’s Bad Jobs into Tomorrow’s Good Jobs

Wearables — Make metallic magic

Electronics — Inadequate volt signal

Biohacking — Arduino Based “Row Bots” Test Rowing Efficiency

Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at !


  1. Looking forward to seeing the rest of the series. Jeri always does informative and entertaining videos. You won’t be disappointed.

  2. Yea! Awesome! I love the work products of both Jeri and Adafruit. So very cool to see them getting together. Also it combines two of my regular-check web sites, reducing web surfing a tiny bit. Looking forward to sharing the series with friends out here.

  3. I Like it.

  4. Looking forward to the rest of the videos!

  5. I like it! 😀

Sorry, the comment form is closed at this time.