The basic principle of an inductively coupled power transfer system is shown in Figure 1. It consists of a transmitter coil L1 and a receiver coil L2. Both coils form a system of magnetically coupled inductors. An alternating current in the transmitter coil generates a magnetic field which induces a voltage in the receiver coil. This voltage can be used to power a mobile device or charge a battery.

电磁感应能量传输系统的基本原理如图1所示，其中包括一个发射线圈L1和接收线圈L2。两个耦合线圈形成电磁感应系统。发射端线圈中的交流电产生的磁场会在接收线圈中产生感应电压。这个电压可以用来为移动设备供电或给电池充电。

The efficiency of the power transfer depends on the coupling (k) between the inductors and their quality (Q). (See also Figure of merit)

The coupling is determined by the distance between the inductors (z) and the ratio of D2 /D. The coupling is further determined by the shape of the coils and the angle between them (not shown).

线圈耦合的强弱是由线圈之间的距离（z）和他们直径之比D2 / D确定的。更进一步，耦合的强弱还与线圈的形状以及它们之间的角度有关。