FIG. 20 is an exemplary view illustrating the heating cause of an external metal material 300 located at the wireless power transmitter 100 according to an embodiment of the present disclosure.
As illustrated in FIG. 20, when a magnetic flux (B) passes through the external metal material (conductor) 300, a current (I) in proportion to a sine value of an angle (Θ) between a surface of the external metal material 300 and the magnetic flux is induced, and the current (I) causes heating in proportion to a resistance value calculated from the resistivity coefficient (ρ) of the external metal material 300.