Question: what is the function of the switch in the electromagnet

title: Electromagnet
text: Both iron - core and superconducting electromagnets have limits to the field they can produce . Therefore , the most powerful man - made magnetic fields have been generated by air - core nonsuperconducting electromagnets of a design invented by Francis Bitter in 1933 , called Bitter electromagnets . Instead of wire windings , a Bitter magnet consists of a solenoid made of a stack of conducting disks , arranged so that the current moves in a helical path through them , with a hole through the center where the maximum field is created . This design has the mechanical strength to withstand the extreme Lorentz forces of the field , which increase with B . The disks are pierced with holes through which cooling water passes to carry away the heat caused by the high current . The strongest continuous field achieved solely with a resistive magnet is 37.5 T as of 31 March 2014 , produced by a Bitter electromagnet at the Radboud University High Field Magnet Laboratory in Nijmegen , Holland . The previous record was 35 T . The strongest continuous magnetic field overall , 45 T , was achieved in June 2000 with a hybrid device consisting of a Bitter magnet inside a superconducting magnet .