Induction hobs heat a cooking vessel electrically by magnetic induction, as opposed to a flame or an electrical heating element.
Cooktops are available as portable units, built-in, or as a full-size oven. They can be used in home or office kitchens, food trucks, convenience stores, restaurants, or in your RV, boat, cabin or dorm room. Some portable induction cooktops are designed only for commercial use.
How Induction Hobs Work
An induction compatible cooking vessel is placed on the glass ceramic surface of the induction cooktop. Underneath the cooktop are electromagnetic coils made from copper wire. When the unit is switched on, an electric current flows through the coils. This produces a magnetic field which generates electric currents in the pot or pan's metal. The base of the pan will be heated directly. Heat is transferred to the food because the cooking vessel acts as a heat source.
The only part of the glass ceramic surface that is heated is where the pot is contact with the induction hob or if there is heat given off by the cookware.
What Cookware Can Be Used on an Induction Hob?
Only ferromagnetic materials such as steel, magnetized stainless steel, enameled cast iron and cast iron work with induction cooktops.
As induction cooktops become more popular in the United States, companies are manufacturing cookware that can be used on conventional stovetops such as electric or gas as well as induction hobs. They simply place a layer of magnetic stainless steel in the base of the cooking vessel. This provides the consumer the versatility of using it on several heat sources.
It is easy to determine if your pans and pots are induction ready or not. Place a magnet on the bottom of your cookware and if it sticks strongly to the base, it is induction ready and can be used on your induction cooker. If the magnet has no pull toward the base of the pot or pan, then it doesn’t have the metals needed to create heat with an induction cooker.
Advantages of Induction Hobs
Disadvantages of Induction Hobs
Induction Cooktop Efficiency
There has been a lot of hype about induction cooktops being much more energy efficient than an electric or gas range. Most people will agree that since heat is transferred directly to the pot, little is lost to the surrounding environment. This means your kitchen won't get so hot, which is great during the summer. In addition, induction cookers heat up faster than electric or gas stoves and react more quickly to temperature changes.
The question as to whether using an induction cooktop is less expensive than electric or gas has been discussed on various review sites and forums. Prior to stating whether the cooking efficiency of induction cooking is or isn't better than electric or gas, I wanted to review the results of a technical assessment that addressed this query. I found one that was conducted by the private firm, Electric Power Research Institute (EPRI). The cooking products used were: full-size gas and electric ranges and two single burner induction cooktops.
Water was heated from 70° to 200° F to conduct the electric and induction tests. Three tests were completed and the results averaged. In terms of electric vs induction, the results showed when the cooking vessel covered the burner, induction efficiency was higher (83.4% vs 77.4%). On the other hand, when the bottom of the cookware was smaller than the heating coil, induction was more efficient, (76.2% vs 41.5%). In the end, the amount you would save on your electric bill is negligible.
Since the EPRI test was conducted on a gas stove at 50°F and on an induction stove at 70°F one cannot make a direct comparison. However, the results do show the efficiency level of gas. When a vessel was used that covered the burner, the gas range was less efficient than induction cooktops (77.4% vs 35.2%). This was also true when the cookware was smaller than the burner (76.2% vs 30.2%). The EPRI finding concluded that the annual induction energy cost is slightly higher than that of gas even when a small vessel is used ($8.49 vs $7.05). 
The History of Induction Technology
The induction cooker was originally produced and put on the market in 1933 at the World’s Fair in Chicago. During the fair, several demonstrations were conducted showing how to use the cooker, along with an explanation of the different types of cookware that can be used on an induction cooktop.
Then, in 1970, more modern developments of induction cooking developed in the United States. Since technology had moved forward, improvements were made and the induction hob became a lot better and more popular with the general public. Westinghouse developed an induction cooker (including matching and compatible cookware) and started selling it to the public. However, there were many problems with induction cooker technology and the idea of them never really took off in the US during this time.
It has only been since the fan noise has been reduced in induction cookers that it has become more popular. While induction cooking failed in the US (during its first few years of being in the market), it thrived in Europe and Asia. As technology advancements in many different areas were taking place, a few companies invested development money in the area of induction technology. Slowly, these products became more well known and understood in the United States. Sales increased when companies reduced the fan noise (although not enough according to some consumers) and manufactured products with fewer reliability issues. The concepts of minimalism and living in small spaces has given induction cooking more visibility. Appliances such as these are of interest to those who prefer a modern looking kitchen as well as those who are curious about products with newer technology.
Induction cooking is an interesting way of preparing your meals. It does take a little getting used to, however, given its benefits, it's certainly something worth considering. The decision as to whether to add a portable single or double burner cooktop, a commercial cooktop, a built-in unit or a full-sized induction range to your kitchen, boils down to your cooking style, budget, and what works best for you.