Magnet , around for ferrite and SmCo, about for NIB and lower for flexible ceramics, but the exact numbers depend on the grade of material. An electromagnet, in its simplest form, is a wire that has been coiled into one or more loops, known as a solenoid. When electric current flows through the wire, a magnetic field is generated. It is concentrated near (and especially inside) the coil, and its field lines are very similar to those of a magnet. The orientation of this effective magnet is determined by the right hand rule. The magnetic moment and the magnetic field of
Is-a has to know about every derivative classes of Shape class. Also, it should be changed whenever new subclass of Shape are created. In object-oriented design, many view the structure of this as anathema. Here is a more subtle example of violation of LSP: This works well but when it comes to Square class, which inherits Rectangle class, it violates LSP even though the is-a relationship holds between Rectangle and Square. Because square is rectangular. The following example overrides two functions, Setwidth and SetHeight, to fix the problem. But fixing the code implies that the design is faulty. The following example,