A bifilar coil is an electromagnetic coil that contains two closely spaced, parallel windings. In engineering, the word bifilar describes wire which is made of two filaments or strands. It is commonly used to denote special types of winding wire for transformers. Wire can be purchased in bifilar form, usually as different colored enameled wire bonded together. For three strands, the term trifilar coil is used.

Some bifilars have adjacent coils in which the convolutions are arranged so that the potential difference is magnified (i.e., the current flows in same parallel direction). Others are wound so that the current flows in opposite directions. The magnetic field created by one winding is therefore equal and opposite to that created by the other, resulting in a net magnetic field of zero (i.e., neutralizing any negative effects in the coil). In electrical terms, this means that the self-inductance of the coil is zero.

The bifilar coil (more often called the bifilar winding) is used in modern electrical engineering as a means of constructing wire-wound resistors with negligible parasitic self-inductance.

Edward Leedskalnin (Latvian: Edvards Liedskalniņš) (January 12, 1887, Stāmeriena parish, Livonia; December 7, 1951, Miami) was an eccentric Latvian emigrant to the United States and amateur sculptor who single-handedly built the monument known as Coral Castle in Florida. He was also known for his unusual theories on magnetism.

(1887 - 1951) Edward Leedskalnin was born January 12, 1887, according to World War I draft registration records, in Stāmeriena parish, Latvia. Little is known of his childhood, aside from the fact that he was not wealthy and achieved only a fourth-grade education. However Edward was a sickly boy, and often spent his time inside reading books - eventually leading him to discontinue his schooling as it "bored him". For Ed, his development of a yearning to obtain knowledge became a passionate and potent driving force in many endeavours throughout his later life. At the age of 26, he was engaged to marry Agnes Scuffs, a girl ten years younger. However, the girl that Leedskalnin referred to as his "Sweet Sixteen" broke the engagement the night before their wedding.