Traveling on airplanes means checking in at airports and having your luggage detect. The machines that perform this duty are typically ....................... or X-ray scanners. The principle of a metal detector involves wire coils, a transmitter and current that creates an electromagnetic field. Any metallic object that enters this electromagnetic field will ................... the current and signal a(n) ........................ . X-ray or CT scanning technology is used to ....................... the density and mass of objects, even their chemical components. In busy airports, large trucks with built-in X-ray scanners are used to scan large amounts of baggage at one time.