Induction cooking: Difference between revisions

An induction cooker uses induction heating for cooking. Usually a ferromagnetic or ferrimagnetic coated pot is placed above an induction coil for the heating process to take place. This type of hob (or, in American English stove top or cooktop) does not work with non-ferromagnetic cookware, such as glass, aluminum, and most stainless steel.

Induction cookers are faster and more energy-efficient than traditional hobs. Additionally, the risk of accidental burning is diminished since the hob itself only gets marginally hot (due to heat conduction down from cookware), allowing direct contact without harm. Also, no heat is lost to the air directly from the hob, keeping the kitchen containing the cooker cooler.

Since heat is being generated from an electric current induced by an electro-magnet, the range can detect when cookware is removed or its contents boil out by monitoring the resistance to the current. In theory, this creates additional functions, such as keeping a pot at minimal boil or automatically turning off when the cookware is removed.

This form of flameless cooking has an edge over conventional gas flame and electric cookers as it provides rapid heating, vastly improved thermal efficiency, greater heat consistency,^[1] plus the same or greater degree of controllability as gas. Water in a pot begins to boil (at its contact points with the pot) in as few as 5 seconds, and then upon turning down immediately (in a second) transitions to simmering.^{[citation needed]}

The amount of time that it takes a pot to boil is proportional to the power or wattage that the induction hob is using. Low wattage induction coils can take as long to heat as the similar wattage in an ordinary electric burner. Thus, the time can be from 3 minutes to around 10 minutes for 3600 watts to 1200 watts induction hobs.

Induction cookers are safer to use than conventional hobs because there are no open flames and the element itself is not hot to the human touch; only the pan becomes hot. Bosch brochures, for example, show a person touching the ceramic cover to the inductor while along side is a pan of boiling water heated by the same induction source.

Induction cookers are also easier to clean because the cooking surface is flat and smooth, even though it may have several zones of heating induction. In addition, food cannot burn onto the cooking serface as it is not hot.

Induction cookers are considerably more expensive than traditional cookers, but consume half as much electricity as electric cookers and are more efficient in heat transfer, achieving an absolute efficiency of 84% in US Dept of energy tests (compared to a typical 40% for a gas cooker).^{[citation needed]} According to CEG Electric Glass Company, "[Induction cooking] power savings of 40-70% are realistically achievable in comparison to conventional cooktops." CEG Electric Glass Company also states induction cooking has an efficiency rate of 90%, while Electric and Gas have efficiency rates of less than 50%.^[2]

Most induction cooking is done on stovetop units, which may be built into a countertop or may be a portable unit. In this style of cooking, the electromagnet is usually sealed beneath a heat-resisting glass-ceramic sheet which is easily cleaned. The pot is placed on the glass coating, and begins to heat up along with its contents. In Japan, a large percentage of rice cookers are powered by induction heating.

In induction cooking, Heat is generated in two ways. In magnetic hysteresis, the rapidly oscillating magnetic field causes power in the magnetic field to be converted to heat in the ferromagnetic base of the pot due to hysteresis. The amount of heat produced is proportional to the area of the hysteresis loop. This is the primary source of heat. With eddy currents, the magnetic field produces electric currents (known as eddy currents) in the metal base of the pot, and these cause resistive heating of the metal.

The heat from the pot is then transferred to the food by conduction, but very little heat is transferred to the actual stovetop. After boiling a pot of water, the surface of an induction stove is slightly warm to touch but not so warm as to burn or even hurt human flesh. Furthermore, within 1 to 5 seconds it cools to room temperature.

However, a pot or saucepan with a copper base or made of aluminium will not work on an induction cooktop. As an induction cooktop relies on the two methods itemised above to generate heat, copper and aluminium, which are not ferromagnetic materials, will perform poorly. Note that eddy currents will be generated in the copper and aluminium, but commercially available induction cooking cannot generate sufficient heat via eddy currents alone in copper and aluminium saucepans for effective heating. Pyrex glass and ceramic containers will not be heated by either method, as such containers are neither ferromagnetic, nor capable of carrying eddy currents.

Market for induction hobs is dominated by German players, such as AEG, Bosch and Siemens. The Italian firm Smeg is also a key player in this market. Prices range from about 400 to 1000 UK Pounds. In 2006, Stoves launched the UK's first domestic induction hob on a range cooker.

Small stand-alone induction hobs are relatively inexpensive, around $100 USD. These units may run 110 volts, which is less than the typical 220 volts in Europe.

Units may have two, three, four or five induction zones, but four is the most common. Some have touch sensitive controls. Some induction stoves have a memory setting, one per hob, that is able to time the amount of heat required.

• Glass-ceramic
• Microwave oven

• US Department of Energy- Technical Support Document for Residential Cooking Products
• PATH Technology Inventory: Induction Cooktops
• Michigan University