John Robert Schrieffer, one of three Americans who shared the Nobel Prize in physics for their theory explaining superconductivity, a near-miraculous process in which electric current flows without resistance, died July 27 at a nursing facility in Tallahassee. He was 88.

Family members confirmed his death to the Associated Press but did not give a precise cause.

Superconductivity, in addition to being one of nature’s puzzles, also offered great promise to daily life when Dr. Schrieffer began his research in the late 1950s. It allowed the large-scale transmission and application of electric currents without the costs incurred in propelling electrons against resistance, even in conducting materials.

Electromagnets depend on the creation of powerful electrical currents. Much modern equipment that requires strong magnetic fields, which are induced by electrical currents, relies on superconducting technology. Even copper wire, one of the best known conventional conductors, can overheat with excessive current, constraining the amount of current it can carry.

Many electrical devices used in medicine and other fields, including imaging devices such as MRI equipment, depend on powerful magnetic fields. These are created through use of extremely high currents, made possible by subjecting them to the low temperatures at which superconductivity sets in.

Among physicists, the theory that accounted for the mysteries of superconductivity became known as the BCS theory, for its three creators: John Bardeen, Leon Neil Cooper and Dr. Schrieffer. They shared the Nobel in 1972.

When the theory was developed in 1957, Dr. Schrieffer was working on his dissertation at the University of Illinois under Bardeen, who had received a Nobel Prize the previous year as an inventor of the transistor. Bardeen also enlisted Cooper, who had just received his PhD and was working at the Institute for Advanced Study in Princeton, N.J.

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Although the phenomenon of superconductivity had been long known, it continued to mystify scientists. A key question involved how and why materials suddenly transitioned from standard conductors to superconductors.

Cooper made a major contribution involving the coupling of electrons into what are now known as Cooper pairs.

In an account prepared by the American Physical Society, an important idea came to Dr. Schrieffer while riding the New York City subway to a physics meeting early in 1957. He realized that all the Cooper pairs in a superconductor could be described by just one of the “wave functions” that characterize quantum mechanics. (Wave functions are essentially mathematical expressions of the idea that matter can exist as both waves and particles.)

The three protagonists of BCS then blended all of their ideas, creating a complete theory. “Well,” the usually taciturn Bardeen was said to have declared, “I think we’ve explained superconductivity.”

Their work was submitted for publication to the Physical Review, where it appeared in December 1957 under the straightforward title “Theory of Superconductivity.”

John Robert Schrieffer was born in Oak Park, Ill., on May 31, 1931. While he was a boy, the family moved to Manhasset, a Long Island suburb of New York, and then to Eustis, Fla., where his father entered the citrus business.

Dr. Schrieffer explored science through work with rockets and ham radio, and entered MIT to study electrical engineering. After two years, he switched to physics, graduating in 1953. He received his doctorate from Illinois in 1957 and worked overseas as a researcher at the University of Birmingham in England and the Niels Bohr Institute in Copenhagen.

He taught at the University of Chicago, University of Illinois and University of Pennsylvania, and in 1980 joined the University of California at Santa Barbara, where he was director of the Institute for Theoretical Physics.

Twelve years later, he moved to Florida State University, where he was chief scientist at the National High Magnetic Field Laboratory before retiring in 2006.

In 1960, he married Anne Grete Thomsen, whom he had first met in Denmark when she was 16, according to a grandson, Maxwell Schrieffer. They had three children, and were happily married for more than half a century, the grandson said. She died in 2013.

A tragic incident shadowed Dr. Schrieffer’s later life, one that his friends found bewildering and difficult to comprehend.

On Sept. 24, 2004, while driving his Mercedes-Benz from San Francisco to Santa Barbara, Dr. Schrieffer slammed into the rear of a van at more than 100 mph. One of the van’s passengers was thrown and killed, and seven others were injured. One of the passengers died a month later. (In a civil suit, attorneys contended that his death was caused by the crash.)

Dr. Schrieffer had nine prior speeding tickets and was driving with a suspended Florida license. He offered a tearful apology in the courtroom, pleaded no contest to a charge of vehicular manslaughter and was sentenced to two years in prison.