A key is provided, including: a magnetic component arranged to generate a magnetic field; a closed loop, herein the closed loop includes a preset device in series connection and a conductor set in the magnetic field; a voltage drop detection chip, herein the voltage drop detection chip has two pins respectively connected to two ends of the preset device and an output port arranged to output a detected voltage drop signal between the two pins; and a key body movably connected on a supporting part, herein the key body is connected to the conductor, the key body can move in two opposite directions on the supporting part, and the key body drives the conductor to cut magnetic induction lines in the magnetic field during motion.