5 Forces That Keep the Universe Together
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5.3 Electromagnetic Force
The second force known to humankind is electricity and magnetism. The
Greeks knew about it in the pre-Christian era. Around 600 BC, they knew
that if amber is rubbed against fur, it acquires the property of attracting small
pieces of materials, such as feather. Later on, this came to be understood that
this happened because of a force called electricity. When amber was rubbed,
it became electrically charged and attracted the electric charges in the other
small object. They also knew about the attractive property of loadstone, which
was later understood as having a magnetic property. It is said that the father
of electricity was William Gilbert, a court physician to Queen Elizabeth I,
who provided an understanding of these phenomena as being due to electric
charges in material. This was in the early 1600, some 2200 years after the Greek
philosopher Aristophanes discovered the electric property of amber. William
Gilbert studied the properties of loadstone and coined the word “magnetism”
and wrote a book entitled “De magnete” as well as other books on the subject.
He concluded that the Earth behaves like a big magnet which is responsible
for making the compass needle point north–south (which previous to that was
believed to be due to the Pole star). Electric and magnetic forces arose from a
new attribute of matter known as the electric charge. The electric forces have
infinite range and become weaker as we move further away from an electric
charge. The electric force law is called Coulomb’s law, after its inventor French
physicist Charles Augustin de Coulomb who published it in 1785. Other giants
whose pioneering works helped us understand electromagnetism better are
British physicist Michael Faraday and Scottish physicist James Clark Maxwell.
Their ground breaking works provided a unified framework for electricity and
magnetism, i.e., that both kinds of forces are part of one and the same physics.
When electric charges are standing still, you only get an electric field, but when
they are moving, you get electric current and associated with it are magnetic
fields going round the current in circles. The story goes that when Faraday
showed some of his experiments on electricity and magnetism to the then
British Prime minister, the prime minister asked “Mr. Faraday, what good is
what you have done” to which Faraday appears to have replied “I do not know
Mr. Prime Minister, but one day you will tax it.”
For a particle to feel the electric force, it must have electric charge or some
magnetic property that is related to the electric charge. Protons, neutrons,
and electrons all feel the electric force and any object that contains them will
obviously feel it too.
37
5.3 Electromagnetic Force
The second force known to humankind is electricity and magnetism. The
Greeks knew about it in the pre-Christian era. Around 600 BC, they knew
that if amber is rubbed against fur, it acquires the property of attracting small
pieces of materials, such as feather. Later on, this came to be understood that
this happened because of a force called electricity. When amber was rubbed,
it became electrically charged and attracted the electric charges in the other
small object. They also knew about the attractive property of loadstone, which
was later understood as having a magnetic property. It is said that the father
of electricity was William Gilbert, a court physician to Queen Elizabeth I,
who provided an understanding of these phenomena as being due to electric
charges in material. This was in the early 1600, some 2200 years after the Greek
philosopher Aristophanes discovered the electric property of amber. William
Gilbert studied the properties of loadstone and coined the word “magnetism”
and wrote a book entitled “De magnete” as well as other books on the subject.
He concluded that the Earth behaves like a big magnet which is responsible
for making the compass needle point north–south (which previous to that was
believed to be due to the Pole star). Electric and magnetic forces arose from a
new attribute of matter known as the electric charge. The electric forces have
infinite range and become weaker as we move further away from an electric
charge. The electric force law is called Coulomb’s law, after its inventor French
physicist Charles Augustin de Coulomb who published it in 1785. Other giants
whose pioneering works helped us understand electromagnetism better are
British physicist Michael Faraday and Scottish physicist James Clark Maxwell.
Their ground breaking works provided a unified framework for electricity and
magnetism, i.e., that both kinds of forces are part of one and the same physics.
When electric charges are standing still, you only get an electric field, but when
they are moving, you get electric current and associated with it are magnetic
fields going round the current in circles. The story goes that when Faraday
showed some of his experiments on electricity and magnetism to the then
British Prime minister, the prime minister asked “Mr. Faraday, what good is
what you have done” to which Faraday appears to have replied “I do not know
Mr. Prime Minister, but one day you will tax it.”
For a particle to feel the electric force, it must have electric charge or some
magnetic property that is related to the electric charge. Protons, neutrons,
and electrons all feel the electric force and any object that contains them will
obviously feel it too.