# How does wireless transfer work?

Answered by Antonio Sutton

Wireless electricity, also known as wireless power transfer, is a technology that allows electrical energy to be transmitted from one device to another without the need for physical connections or cables. The concept itself is quite simple: a transmitter generates an alternating current (AC) which is then converted into a magnetic field. This magnetic field can then be picked up by a receiving device, which converts the magnetic energy back into AC.

The key component in wireless power transfer is magnetic resonance energy transfer (MRET). This is the process by which the magnetic field generated by the transmitter is efficiently transferred to the receiving device. MRET relies on the principle of resonant coupling, which occurs when two objects have similar natural frequencies and can exchange energy efficiently.

To understand MRET better, let’s break down the process into a few steps:

1. Transmitter: The transmitter is responsible for generating the AC current and converting it into a magnetic field. This is typically achieved using a coil of wire, often referred to as a primary coil, which is connected to a power source. When an alternating current flows through the primary coil, it creates a changing magnetic field around it.

2. Magnetic Field: The changing magnetic field generated by the primary coil extends into the surrounding space. This field is what enables the wireless transfer of energy. The strength and range of the magnetic field depend on factors such as the size and shape of the primary coil, the amount of current flowing through it, and the frequency of the AC.

3. Receiving Device: The receiving device, also known as the secondary coil, is designed to pick up the magnetic field generated by the transmitter. It consists of another coil of wire, which is connected to the device that needs to be powered. The secondary coil is specially designed to have a resonant frequency that matches that of the primary coil, allowing for efficient energy transfer.

4. Magnetic Resonance: When the secondary coil comes within the range of the magnetic field generated by the primary coil, a phenomenon known as magnetic resonance occurs. The secondary coil absorbs the energy from the magnetic field and converts it back into AC. This AC can then be used to power the device or charge its batteries.

It’s important to note that wireless power transfer is not limited to a single transmitter and receiver pair. Multiple devices can be powered simultaneously by using multiple primary and secondary coils, as long as they are within the range of the magnetic field.

Wireless power transfer has been a topic of interest for over a century, but it took time for the technology to become practical and commercially viable. One of the challenges was finding efficient ways to transfer energy over longer distances without significant energy loss. Another challenge was ensuring the safety of wireless power transfer, as strong magnetic fields can interfere with electronic devices and potentially be harmful to living organisms.

In recent years, there have been advancements in wireless power transfer technology, with the development of resonant inductive coupling and other techniques. These advancements have made it possible to transfer power over greater distances with higher efficiency, paving the way for applications such as wireless charging of smartphones, electric vehicles, and even wireless powering of medical devices.

Wireless power transfer works by converting AC into a magnetic field using a transmitter and then picking up that field with a receiving device, which converts it back into AC. Magnetic resonance energy transfer plays a crucial role in efficiently transferring the energy between the transmitter and the receiver. While the concept is simple, the challenges of efficiency, safety, and distance have been major factors in the development and commercialization of wireless electricity technology.