where represents the 'free current' enclosed by the loop so that the line integral of does not depend at all on the bound currents. For the differential equivalent of this equation see Maxwell's equations. Ampere's law leads to the boundary condition:
where is the surface free current density.
Similarly, a surface integral of over any closed surface is independent of the free currents and picks out the 'magnetic charges' within that closed surface:
which does not depend on the free currents.
The -field, therefore, can be separated into two independent parts:
where is the applied magnetic field due only to the free currents and is the demagnetizing field due only to the bound currents.
The magnetic -field, therefore, re-factors the bound current in terms of 'magnetic charges'. The field lines loop only around 'free current' and, unlike the magnetic field, begins and ends at near magnetic poles as well.
Forehead
The forehead of humans is the flat space of skin above the eyes, between the eyebrows and where your hair starts to grow. It exists to make room for the brain inside the skull.
A doctor or nurse will often touch someone's forehead to check whether or not they have a fever. This is because of the many blood vessels in the head and face.
In ancient Greece individuals with large foreheads were classified as intellectual because of their incredibly large "brain". Nowadays this is not the case.
According to the OED Forehead can be pronounced either 'forhed' or 'forrid'.
'Forrid' used mostly around the Isle of Sheppey area.
James Prescott Joule
James Prescott Joule (24 December 1818 – 11 October 1889) was an English physicist, born in Salford, near Manchester. In his time he had great contribution to the world of electricity and thermodynamics. He was best known for discovering Joule's law, which described electric heating by saying the amount of heat produced each second in a conductor by a current of Electricity is proportional to the resistance of a conductor and to the square of the current. The unit for this is joule, equal to one watt-second. Later Joule worked with William Thomson to find out that the temperature of gas falls as gas expands. This principle was then known as the Joule-Thomson effect.
The son of Benjamin Joule (1784–1858), a wealthy brewer, James Prescott Joule was born in the house next to the Joule Brewery in New Bailey Street, Salford on 24 December 1818. James was tutored at the family home 'Broomhill', Pendlebury, near Salford, until 1834 when he was sent, with his elder brother Benjamin, to study with John Dalton at the Manchester Literary and Philosophical Society. They only received two years of education in arithmetic and geometry before Dalton was forced to retire because of a stroke.
Kinetics is the science of motion. Joule was a pupil of Dalton and it is no surprise that he had learned a firm belief in the atomic theory, even though there were many scientists of his time who were still skeptical. He had also been one of the few people receptive to the work of John Herapath on the kinetic theory of gases. He was further greatly influenced by Peter Ewart's 1813 paper "On the measure of moving force."
Andromache
Andromache is a person in Greek mythology. She is the wife of Hector of Troy and mother of Astyanax.
After the Trojan War, Neoptolemus took her and Helenus as slaves. Of Neoptolemus she had a child named Molossus. After Neoptolemus died, Andromache married Helenus, and became Queen of Epirus.
Astyanax
Astyanax is a person in Greek mythology. He is the son of Hector of Troy and Andromache. He is killed at the end of the Trojan War by Neoptolemus, so he could not be a new king of Troy, or want revenge.
Neoptolemus
Neoptolemos (or Latin Neoptolemus) is a person in Greek mythology. He is an important person in the Trojan War.
Neoptolemus was the son of Achilles and Deidamea. He was needed to win the Trojan War. He killed King Priam and Astyanax, sacrificed Polyxena to his dead father Achilles, and took Helenus and Andromache with him as slaves.
He was later killed by Orestes because he was going to marry Hermione, who Orestes wanted for himself.
Earth's orbit
All planets in our solar system follow an elliptical path. This path is known as an orbit. Earth's orbit is not a perfect circle. If we were to draw the Earth's orbit on a sheet of paper as a perfect circle, the width of the line would be larger than the elliptical path of the Earth.
The Earth's orbit takes about 365 days, this is also called a year. This means that in 365 days (a year) the Earth has gone around the Sun. From this we can find that the orbital speed of the Earth is about through space.
The closest distance Earth is to the Sun, or perihelion, is and the farthest or aphelion is . It takes light (or any other electromagnetic radiation) just over eight minutes to travel from Sun to Earth.
The seasonal changes on Earth are because of the 23.44° axial tilt of its rotation and slightly elliptical path around the Sun.
The orbit varies over long periods of time according to the Milankovitch cycles. These cycles are one of the main causes of climate change.
Penelope
Penelope is a person in Greek mythology. She is the wife of Odysseus of Ithaca and mother of Telemachus. She became a symbol for the faithful wife.
When her husband Odysseus was on his long journey home, many people thought he was dead. Because of this many suitors came who wanted to marry Penelope, because then they would own her land and wealth, and become king of Ithaca.
Penelope thinks of several tricks so that she does not have to marry one of the suitors. One trick is that she tells the suitors that she will first weave a cloth for the funeral of Odysseus' father, and when she was finished she would marry one of the suitors. But every night she undoes her weaving again, so that she never finishes it.
When Odysseus finally comes back after twenty years, he and his son Telemachos kill the suitors.
Anemia
Anemia (U.S. spelling) or anaemia is not having enough red blood cells or hemoglobin in the blood.
"Dimorphic anemia" means two types of anemia at the same time. For example, macrocytic hypochromic, due to hookworm infestation leading to not enough of both iron and vitamin B12 or folic acid or following a blood transfusion.
Memphis, Tennessee
Memphis is the second-largest city in the state of Tennessee. The city has a large port on the Mississippi River. It is also well known for blues music and barbecue. The city is also home to FedEx, a leading company that ships packages around the world. Memphis is also known for being the home of rock and roll legend Elvis Presley.
Memphis is named for Memphis, Egypt, an ancient capital city of Egypt.
The future area of Memphis was first settled by the Mississippian Culture before it was discovered by French and Spanish explorers.
The United States took the land from Spain in 1797, and Andrew Jackson implemented the Indian Removal Act that facilitated the expulsion of the Cherokee from the area, making it available to white settlers. The city was established in 1819. Until the American Civil War, Memphis was a hub of cotton and slave trade. Brutal riots of angry whites against black people took place in 1866, in which 46 African Americans were killed. Yellow fever struck the city in the 1870s, killing a lot of people. The city recovered, and its population more than doubled.
The Memphis sanitation strikes was one of the key movements in the Civil Rights Movement. Musicians such as Elvis Presley, Johnny Cash, Jerry Lee Lewis and B.B. King influenced the city's identity as the birthplace of rock and roll.
Memphis is located east of the Mississippi River. The Wolf River, a tributary of the Mississippi River, crosses the city.
Its metropolitan area extends into Arkansas and Mississippi.
Jim Strickland is the Mayor of Memphis.
Dari (Eastern Persian)