Joseph Henry and What is a Magnetic Field?

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Joseph Henry was one of the giants of American history. When we look at inventors from the past, there are not many out there more significant and more influential than Joseph Henry. His work is unprecedented, and he was an expert in many fields. 

His most notable and essential work comes in the form of electromagnetic induction, which we will cover in more detail in the second part of this article. He also had a notable influence on aeronautics, electronics, the telegraph, and in many more fields. He was also a major proponent of American science and was one of the most influential personalities that inspired American scientists to make many discoveries. He was the first Secretary of the Smithsonian Institution.

It is fair to say that Henry possessed both talent and practical abilities, which is almost a guarantee for success. He devoted his life to education, knowledge, and invention. Today, we can admire his life achievements and his greatness from afar because we are still under the influence of his work. His discoveries enabled us to live the way we do today, and in many ways, his work is still relevant. For now, let us focus on the mind of Henry and his genius. In the second part, we will focus more on his significant life achievement: his work in electromagnetism and work with magnetic fields. 

Who was Joseph Henry, and what is a magnetic field?

The Life of a Genius

Joseph Henry’s life was so full of achievements that it is hard to choose the right place to start. While we could start talking about his work in magnetism, or about his work in science, it is vital to know the background of a man who was so influential. We will start the story of Joseph Henry in his early years – how he grew up, what drove him to become an inventor, how did he achieve this? And lastly, we will analyze the story and see what lessons are there to learn from Joseph Henry and his life.

Joseph Henry (December 17, 1797 – May 13, 1878)

Born to a Poor Family

Joseph Henry was born on the 17th of December in 1797 in Albany, New York. His parents were of Scottish descent; Joseph’s father, William, was a laborer, so he was quite poor. Joseph was unlucky; at the age of eight, his father died and was sent to live with his grandmother in the town of Galway, located about 40 miles from Albany. Henry was reliant on his grandmother to support his education. Even though, as a young man, he was very keen to learn, he only got as far as elementary school due to his family’s financial situation.

Young Joseph did not give up. His desire to learn new things was so strong that he started an apprenticeship as a watchmaker. Although this was not his desired field, as he later learned, he gained many critical practical skills as an apprentice. He had many interests by the time when he was 16. His first real passion was to become a professional actor. That is until he read a book called “Popular Lectures on Experimental Philosophy.”

That book was the spark that ignited the fire within Henry; sometimes, all we need is a little inspiration. Henry started reading scientific books religiously. It was during this time that Henry learned the essentials of practical science and experiments. He would begin doing experiments and calculations, which added a practical layer to his knowledge.

Education and Work at The Albany Academy

Henry’s talent was soon recognized at the Albany Academy. He was so skilled that he received ted free tuition starting in 1819. He would occasionally help teachers with lectures and provide tutoring for other students in science. Henry matured quickly that eventually, he would assist professors with lectures and even start doing some on his own.

He started working at the Academy as a professor in 1826; initially, he began teaching mathematics and natural philosophy. He spent his entire days at the Academy, first giving lectures to students and whole afternoons researching and doing experiments. It was during this time that he started learning about magnetism and focused most of his time on this subject. Henry was apt in many fields of study. His knowledge included mathematics, science, magnetism, philosophy, physics, chemistry, as well as many other fields.

This time in his career was undoubtedly crucial, as he learned many interesting concepts and was able to carry out many experiments. In 1831, he began his work in electromagnetism. He attended a lecture on magnetism conducted by William Sturgeon, where he discussed his concept of the electromagnet. Joseph saw room for improvements. He wanted to make it more powerful, which he quickly did by coiling insulated wire around an iron core.

Another achievement during this time came when he built an electromagnet that was used to separate iron ore. This device proved to be very efficient at separating the iron from dirt in mines and was the first commercial use of electricity.

Joseph Henry is often credited with the discovery of inductance, but other scientists like Michael Faraday also worked on the subject. His work in electromagnetism enabled many improvements that made the invention of the telegraph feasible. We will discuss his contributions to electromagnetism in the second part of the article.

Move to the College of New Jersey

In 1832, Joseph Henry was offered a reputable position at the College of New Jersey. Joseph reluctantly accepted a job as the First Chair. After thirteen successful years at the Albany Academy, he moved to New Jersey to embark on a new adventure in his life.

Henry enjoyed a lot of freedom at the College of New Jersey (later Princeton University). During this time in his life, he became interested in the research conducted in other nations. He was particularly interested in the field of science in Europe. It was during a College funded trip to Europe, where the American was to meet some very influential scientists. The most notable scientist he met was Michael Faraday. It was from him that Joseph Henry became familiar with new concepts, new scientific approaches.

His time at the College was fruitful in terms of his work. His idea of a telegraph was born from this new knowledge. Henry was known to use the telegraph for even the most mundane tasks. Such as ordering lunch and calling in from his campus to the laboratory. But Joseph did not make his telegraph invention public and instead, was later claimed by Samuel Morse. Henry described his time at Princeton University as a time when he “made several thousand original discoveries regarding electricity, magnetism, and electromagnetism.”

While at the College, he developed a very fruitful working relationship with his assistant, Sam Parker. This relationship was an exciting development for the time because Sam Parker was a free black man. He was hired on behalf of Princeton University to help Henry conduct his experiments and let him focus on studying and developing new concepts. Parker made work for Henry much more enjoyable. He did all the dirty jobs for Henry, at least that is how Henry described it. Parker would provide Henry with materials, clean up his laboratory, and fix technical issues on the machinery. There are even claims that Sam Parker acted as a test subject for Henry’s lectures and experiments.

Joseph found plenty of time to do various experiments in many different fields. In addition to electromagnetism, he also studied and performed experiments in ballistics, acoustics. He also did studies of sunspots. His work proved to be invaluable for later discoveries – many of them were based on Henry’s work.

Joseph Henry statue at the Smithsonian Institution

The Most Prominent American Scientist

In 1846, Henry was offered an exciting position as the First Secretary of the Smithsonian Institute. Henry thoroughly enjoyed his time at the College of New Jersey, as he said himself, and was very reluctant to leave his position. His time at Princeton was perhaps the most fruitful time of his life. He was allowed great creative freedom. There he had all the tools and the requirements to do experiments and study new things. But the position at the Smithsonian Institute turned out to be too good to turn down.

Joseph Henry was chosen for this position by a committee because he was the most important and the most prominent American scientist at the time. Even though this position did not allow Henry to do what he loved most, he was pleased to accept this new challenge. He became an icon and the image of success through American science and ingenuity. 

During his time at the Smithsonian Institute, his job would be to represent American innovation all around the world. While also promoting science to young people and encouraging them to join the field. He became a great leader of the new generation of American scientists.

Henry was, in fact, one of the men that proposed the introduction of the Smithsonian Institute. He thought that the knowledge of scientists was spread out and unorganized. He wanted to create an institution that would connect all American scientists through funds, projects, and publishing reports in the scientific literature. This united all scientists, but also supported them and enabled them to reach the masses.

Henry was essential for many subsequent discoveries and inventions that occurred during this time. He supported scientists and inventors, which would lead to more important discoveries. 

Henry worked with Stephen Alexander in 1848 on his project in the study of sunspots. Together they determined that the area around sunspots is cooler than other areas on the sun’s surface. He also promoted the telegraph and supported the building of telegraph lines all over the country. Henry also got involved in predicting weather and warning the general public about incoming weather patterns. For this, he led a team of six-hundred volunteers that helped him observe weather conditions and provide reports from various areas in the country.

Perhaps his most notable collaboration at this time was his support for Alexander Graham Bell. Joseph Henry encouraged and supported Bell to invent the telephone with the help of the science that was developed by Henry. Bell wanted to create a machine that would transmit the human voice from the speaker to a receiver, but he thought that he did not possess enough knowledge to do so. Henry encouraged Bell to get the understanding by saying the words: then go “Get it.”

He was also influential in aeronautics. Joseph Henry would help and collaborate with Thaddeus Lowe, to create a gigantic balloon. Their work would turn out to be essential for the industry. Henry’s knowledge, wisdom, and experience were highly rated during the Civil War. He also served as a technical advisor to Abraham Lincoln.

Family life

Joseph Henry married his cousin Harriet Alexander in 1820. Together, they had six children; two of them died in infancy. Henry is thought to have spent little time with his family and spent the majority of his time working and studying.

Later Years – Death and Legacy

In the late years of his life, Henry was still somewhat involved in science. Many scientists sought Henry’s advice during this time, including Alexander Graham Bell. His knowledge and wisdom continued to inspire many scientists. He was still actively advising people with the research up until the end of his life.

Joseph Henry died on the 13th of May 1878; He rests at the Oak Hill Cemetery in Washington, DC. He left an extraordinary legacy behind him. It was his work that graced the world with electromagnets, electromagnetic induction, the telegraph, one of the first electromagnetic motors, and the electric relay. 

His work helped the design of the telegraph and, later, the telephone. He influenced many areas of research, including aeronautics, meteorology, lighthouses, and more.

Magnetism and Joseph Henry

Due to the abundance of his work in electromagnetism, we will devote this whole chapter to Henry’s most important work. We will try to understand some of the concepts in this field of study. How do magnetic fields work, and how did Henry take its advantage for his inventions?

Joseph Henry and his Work With Magnets

Henry started being intrigued by magnets at a relatively young age. He began studying the magnetic field as early as in his childhood. He read various science books, where he gained a lot of knowledge. But his main work with magnets came after he started working at the Albany Academy and later when he was at Princeton.

Henry started taking an interest in terrestrial magnetism and magnets in general while at the Albany Academy. After he finished a lecture, he would begin doing experiments with magnets. Henry was possibly heavily influenced by other scientists for their work in magnetism at this time. He attended a lecture by a British scientist named William Sturgeon in 1830. Sturgeon sought to improve electromagnets and make them more powerful. During the lecture, Sturgeon described how he coiled uninsulated wire around an iron core to increase an electromagnet’s strength.

Henry saw plenty of room for improvement in Sturgeon’s design. He thought that the wire should be insulated and wrapped more closely to the core. That would significantly increase the strength of the magnetic field and, consequently, the power of an electromagnet. 

His experiments proved to be highly successful. Henry’s magnets were much more potent than those of Sturgeon, which he often demonstrated to his students and at Yale University. Initially, his magnets could lift as much as 2.000 pounds, and were later improved to raise more than 3.500 pounds.

Henry’s discovery would have a significant impact on later developments in the electromagnetic field and inventions. But he was not the only one who developed a strong electromagnet. His contemporary, Michael Faraday, developed a strong electromagnet at about the same time as Henry. Faraday got the credit for it, as Henry did not publish his work. But many people believe that Henry discovered it earlier than Faraday.

What is a magnetic field?

Henry’s invention of his powerful electromagnets is a credit to his genius, but also his persistence and years of experimentation with magnetic fields. To better understand his concept of electromagnets, we must first take a look at how a magnetic field works.

Henry dealt mainly with electromagnets; these types of magnets produce a magnetic field with the help of an electric current. The magnetic field is only active when an electric current is present. As soon as the current is turned off, the magnetic field disappears. Electromagnets are different from regular magnets in this respect. Regular magnets do not require electrical current to produce a magnetic field. 

The advantage of Henry’s electromagnets at the time was that they were able to create much stronger magnetic fields than regular magnets. In addition, they have the ability to control the strength of the magnetic field via an electric current.

Now we must note that Henry was not the first scientist who invented an electromagnet; it was designed much earlier in 1824 by William Sturgeon. Some concepts of electromagnets date back to 1820. What made Henry’s invention so significant is the fact that he made them much more potent with some minor but smart improvements. These modifications made them much more effective at their job than earlier designs.

Henry’s electromagnets were significantly more powerful because he wrapped many layers of silk thread insulated wire around an iron core. While the insulation kept the electrical power from shorting out, the multiple layers of wires allowed the electromagnet to produce powerful magnetic fields. Most importantly, this made electromagnets suitable for commercial use.

The magnetic field created by a permanent magnet.

How do magnetic fields work?

The magnetic field around the electromagnet works the same way as it does for regular magnets. The only difference is that the strength of the magnetic field can be increased or decreased by adjusting the electric current. 

A magnetic field is a concept; it is a way of describing how magnetic force flows around a magnetic object. A magnetic field is a vector field where vectors travel to the poles of the magnet. A magnet has two poles: a north and a south pole. The vector lines represent the magnetic force that moves to the poles of a magnet. Thicker vector lines represent a stronger magnetic current. Where the magnetic force is stronger, these vector lines usually bunch together – the density increases.

An electromagnetic field works similarly to a magnetic field, only that it is a combination of electric and magnetic fields. In electromagnetic fields, the fields get their influence from the electricity that is produced by the power source. The source of electricity can be an electrical socket, a battery, or an electric generator. In addition to the number of turns in the coil, the greater the amount of electricity produced, the stronger the magnetic field will be. 

Henry’s electromagnets enable the invention of the telegraph

Joseph Henry’s invention of stronger electromagnets later proved to be vital for the invention of the telegraph. He also managed to create some significant designs that would then change the world. Using his knowledge, Henry was able to develop machines that used electromagnets to create motion. These machines were very powerful for the time. These are also the earliest known concepts for a DC motor. Joseph Henry can, therefore, take credit for the invention of the electric motor. The machines allowed Henry to observe another interesting idea that he would end up working on – self-induction.

Electromagnetic inductance is another concept that was worked on by Henry. Faraday also studied it at about the same time, so he was later credited for its invention. Inductance is an important concept that would allow scientists to create robust machines using the power of magnetic fields. 

What is inductance? An electrical conductor tends to react to the change of the electric current and create a magnetic field when the current flows through the conductor. When the strength of the electric current changes, so does the magnetic field. And this change of the magnetic field can create enough motion for a machine to work efficiently. This motion is also called electromotive force.

Henry’s electromagnets were well-suited for these machines, as they had enough coiling to make them very powerful. Even though Henry did not receive credit for the discovery of inductance, he was undoubtedly one of the first to consider it in real-world applications.


Henry was one of the greatest scientists and inventors not just in America, but from anywhere in the world. His talent, determination to learn new things and experiment and to learn made him an expert in many fields. What can we take away from Henry’s life and his achievements?

  • Learn something new each day. 
  • Seek inspiration from other people.
  • Try new things and experiment. 
  • Create inventions that can be used by people.
  • Determination is the key to success. 

Are you ready to become an inventor?

Getting your idea out of your head and into your hands is only the first in a long set of steps towards becoming a successful inventor.

First Steps To A Successful Invention

At Invention Therapy, we believe that the power of the internet makes it easier than you think to turn your invention idea into a reality. In most cases, you can build a prototype and start manufacturing a product on your own. Changing your way of thinking can be difficult. Being an inventor requires you to balance your passion with the reality of having to sell your products for a profit. After all, if we can't make a profit, we won't be able to keep the lights on and continue to invent more amazing things!

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