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.
Solenoids and electromagnets technically are not the same thing, but people talk as if they are. A solenoid is just a coil of wire, but when you run a current through that coil of wire, you create an electromagnet.Since this is, by far, the most useful application of a coil of wire, it's not surprising that when you say the word 'solenoid' people tend to assume you mean electromagnet.olenoids are most commonly used as electromagnets, and all the examples so far are that kind of solenoid. But there are some other uses. They can be used to slow the flow of electricity in a circuit, making them an example of an inductor, or an impedance device.