By holding a magnetic coil over somebody's skull, a researcher can affect the activity of the piece of cortex beneath, while causing no pain to the subject.

ECONOMIST: The ethics of brain science

That is because the transmitter uses a large flat coil, placed over the heart, to generate the magnetic field that powers the receiver.

ECONOMIST: Case history

With more than 700 patents to his name, Tesla invented radio, the coil transformer, wireless communication, fluorescent lights and the alternating-current motor, which allowed electricity to flow over long distances.

FORBES: Pioneers Die Broke