the citadel or high fortified area of an ancient Greek city. the Acropolis, the citadel of Athens and the site of the Parthenon.
Electromagnets are used in a number of everyday devices. One useful characteristic of an electromagnet is the fact that you can vary its magnetic force by changing the amount and direction of the current going through the coils or windings around it.ummary. Electromagnets are used in a number of devices, such as loudspeakers and tape recorders. Some electromagnets can be very strong and its power can be readily turned off and on, such as in junk yard electromagnets and electromagnetic locks.
Magnetometers are used to measure the strength of the magnetic field and in some cases direction of the field. These come under scientific instruments. A sensor which is attached to this device measures the flux density of the surrounded magnetic field around it.agnetometers are used to measure the strength of the magnetic field and in some cases direction of the field. These come under scientific instruments. A sensor which is attached to this device measures the flux density of the surrounded magnetic field around it.