The document contains 4 case studies related to automotive electrical systems: 1) The central locking solenoid system uses electromagnetism to open and close vehicle locks when buttons are pressed. 2) Methods for reducing electromagnetic interference in ignition systems include resistors, bonding of vehicle parts, and screening of ignition components. 3) AM radio transmits information by varying signal amplitude while FM radio varies frequency. FM radio has better sound quality due to less interference. 4) Radar systems determine position of other vehicles by transmitting radio waves, measuring the weak signal scattered back, and calculating distance and direction based on radio wave speed.