A nonpolarized electromagnet doesn't use a permanent magnet. Examples of nonpolarized battery-operated electromagnets include items such as door bells, door locks and circuit breakers. This type of electromagnet uses a solenoid, which is an electrically operated metal piston. The piston is inside a metal tube, which has a wire tightly wrapped around one end. When an electric current passes through the wire, it creates a magnet and draws the piston towards the end of the tube that has the wire wrapped around it. As soon as the electric current stops, the piston goes back to its original position because the magnetic field dissipates.
Nonpolarized electric motors operate by inducing a magnetic field in several places. The motor has several wire windings fixed to the internal casing of the motor. A central spindle, known as an armature, runs through the center of the casing, which also has wire windings wrapped around it. When a current passes through the outer windings and the armature, opposing magnetic fields are created. This forces the armature to start rotating. As the electric current increases through the windings, the magnetic force increases, making the armature rotate faster.
Polarized electric motors use permanent magnets fixed to the internal part of the motor's casing instead of wire winding. This means that there is always a magnetic field present. However, the armature is exactly the same as a nonpolarized electric motor's armature. Current only needs to be passed through the armature to make it rotate. Current isn't passed through the permanent magnet. Polarized electric motors are not generally as powerful as nonpolarized motors.
You can't see or feel electromagnetic waves, but they are everywhere. It's how you listen to the radio, watch TV, and if you use a microwave, they heat and cook your food. Electromagnetic waves vary in size, known as wavelengths. Radio waves are long, up to the length of a football pitch; microwaves are medium-size, about the size of a large insect; while infrared waves are very short, perhaps the size of bacteria. The longer the wave, the farther the distance it can travel. As with all electromagnets, if you turn off the electric current, they disappear.