While waiting to board a flight last week, I browsed the airport's newspaper/souvenir shop, selecting the June 2011 issue of Automobile magazine for my in-flight entertainment. This article about the experimental Rolls-Royce 102EX Phantom experimental electric car caught my eye.
Inductive charging is already used to charge things like iPhones, mp3 players, game controllers and electric toothbrushes. But how does it work?
[Funny physics-related Powermat commercial.]
Inductive charging takes advantage of the electromagnetic (EM) field, one of the fundamental forces of nature along with gravity, the strong interaction and weak interaction. When electricity passes through a wire, it creates a magnetic field surrounding the wire. Winding the wire into coils makes a larger magnetic field.
Charging mats, like the Powermat or the Getpowerpad pictured at right, contain a series of coils embedded in the mat. The coils produce an electromagnetic field that's strong enough to charge electronics but too weak to hurt people.
When you put a free-floating coil near the coils in the pad, the magnetic field induces a current in the free-floating coil that is used to charge a battery. For electronics that don't have a coil embedded, an adapter - like the Getpowerpad one attached to an iPhone at left - connects a coil to an object's battery.
For the Rolls, charging the battery completely via induction takes about 20 hours (yikes!), about the same as charging it the old-fashioned way (can we say that yet?) - via the plug. That charge gives the 389 horsepower luxury behemoth a range of 125 miles - not as good as the average bear but enough to get you to work and back.
The only problem is that it will take more than one night's repose to recharge the thing. Oh well, just take the Rolls to work every other day.
Perhaps when you and I are old and gray, we'll be free of wires. Re-charging mats will be standard in our garage floors and kitchen counter tops and EM coils will be embedded in all major roadways, charging cars on the go. But by then, of course, the robots will have taken over and we'll no longer need cars. But I digress...