Joseph Henry: Biography, Inventions & Contribution

Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

Joseph Henry was one of Americas most regarded and celebrated scientists. We are going to look at his life as well as the discoveries, inventions and contributions that he made to earn such respect.

Joseph Henry

Many intelligent scientists have contributed to the field of science and our lives. Joseph Henry, an 1800's innovative physicist, is one of those scientists. Joseph Henry was born and raised in upstate New York by Scottish parents. Have you ever heard the saying, ''Everything isn't for everybody?'' Well, Joseph decided that school was not for him at the age of 13. So, he didn't focus on learning and instead became an apprentice to a watchmaker. Now, how is this young man shaping up to be a scientist?

Joseph Henry was one of the greatest American scientists.
Picture of Joseph Henry

Well, after Henry's dad died, his mom took in boarders to make money. One boarder gave Henry a book that piqued his interest in learning. After that, he focused on learning as much as he could about nature. This decision to focus on learning led him to excel as a student and go on to attend Albany Academy, where he would eventually end up teaching and doing research as a professor. That's how you turn your life around! He made some major discoveries and had wonderful inventions that are still in use today.


Henry was very interested in electricity and magnetism, so that is where he focused his research. Other scientists during Joseph Henry's time already figured out that they could use electrical currents to create magnetism and that copper wire wrapped around an iron core could hold magnetism for a very short time. Henry entered this area of research and discovered that isolating the copper wires by wrapping them in silk before wrapping them around the iron core allowed the wires to hold their magnetic field for an extended time.

Joseph realized there is a relationship between electrical currents and magnetic fields. He wondered if the relationship goes both ways. His first discovery used electric currents to create magnetic fields. But, could magnetic fields create electric currents? He discovered the answer is yes! Henry moved magnets to create a moving magnetic field which generated electrical currents. This discovery became known as electromagnetic inductance. Electromagnetic inductance has had far reaching impacts on our lives today since it is used in almost every type of electric power plant.

Henry furthered his discoveries in electromagnetic inductance by discovering that opposing currents occur in a wire if the amount of electric current going through the wire changes causing a change in the magnetic field. Since the changes cause currents that are opposite of each other, this negates the initial change in the amount of electrical current and therefore allows the current to remain unchanged. This phenomenon is known as self-induction.

While Henry was looking at changes in electrical currents and magnetic fields, he also discovered mutual induction. Mutual induction is when a change in current in one wire causes changes in the magnetic field resulting in electrical currents being induced in nearby wires. With the work that Joseph Henry put into electrical inductance, it was only fitting for the unit of measurement for electrical inductance to be named the henry. You will see this abbreviated as just H when written down next to a measurement.


Joseph Henry did more than discover information about electricity and magnetism. He incorporated his discoveries into some very key inventions. The first electromagnet was invented around the time that Henry was making discoveries. The problem was that the electromagnet was not very strong and could only hold up to 9 pounds. That's not very much. When Joseph used his discovery of insulating wires and combined that with using multiple short pieces of wire to increase the magnetic field, he invented the world's strongest electromagnet. It could lift up to 750 pounds. This electromagnet became known as the Albany magnet.

One of Henrys earliest electromagnets
Picture of the electromagnet

With continuous adjustments, Joseph increased the strength of his electromagnets to the point where they could lift and hold up to 3300 pounds. Scientists and universities all over the country wanted him to make powerful magnets for them. The one that could hold over 2000 pounds was requested by Yale University and was named the Yale magnet.

Joseph Henry needed pure iron ore to continue making his highly requested electromagnets. An iron works company in NY needed a way to get pure iron ore as well. So, Henry created an ore separator to sort through iron and get the purest pieces for his magnets. Of course, the device used electricity generated from magnets. This was the first commercial electrical device invented.

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