Metal Detectors

Lately we have been learning a lot about magnets. On the past test, we were asked how metal detectors work. Although I am not completely sure, I know that it has something to do with magnets. Metal detectors use electromagnetic induction to detect metal that passes through them. Inside the metal detector is a coil. A current is passed through that coil to create an alternating electromagnetic field. When metal passes through the detector an alternating magnetic field is formed around that metal. Another coil detects the field of the metal that passes through the detector. After thinking about how metal detectors work, I thought about this past summer when I visited Vietnam. We caught many flights around the country but before returning to Hawaii, we stopped off in Japan. One of my friends decided to buy Cuban Cigars as a gift for his dad since you can't get them legally in the U.S. He bought them at the airport he had to carry them on. He left them in his pocket when we went passed security and the metal detector beeped. This was an indication that there was metal in the packaging that set of the alarm. Now I have a better idea how exactly that metal triggered the alarm.