Induction cookers allow you to heat up your meals much faster, more safely and more efficiently than standard electric stoves or gas cookers. But how exactly can it do this?
Remember that essentially cooking is the application of heat to food. However, for the most part, food is hardly ever heated directly. Instead, the cooking vessel is heated up, indirectly applying heat to the food which is contained inside. In the process, a lot of the heat, or thermal energy, is wasted as a great deal of it never comes into contact with the food.
An induction cooktop uses this same tried-and-tested method, but in a slightly different way to the usual gas or electric means, and with a smart alteration which means less energy is wasted.
Also See: portable induction cooktops
An induction hob cooktop an incredibly powerful, generally 24 kHz high-frequency electromagnet, designed to create an electromagnetic field which goes on to rapidly and directly heat up the entire lower surface of your pots and pans.The food inside your cookware is therefore heated a great deal more evenly than it would be heated by an electric stove or gas flame. Due to this electromagnetic field, the cookware is therefore the original generator of the heat that is then directly used for cooking your food. In other words, the heat is directly generated in the cookware rather than in the cooker itself.
In order to create this miraculous electromagnetic field, a high frequency AC electrical charge passes through a copper coil which runs under the cookware. The fluctuating alternating current brings about magnetic flux, ultimately heating the metal cookware.
The induction element generates a magnetic field which induces, or transfers, the energy into the metal, converting electrical energy into thermal energy.
The cookware does have to be metal, generally one containing iron such as certain types of stainless steel. These materials are known as ferrous metals. Generally, if the metal cooking surface is going to be suitable for induction cooking, it will also be magnetic. Therefore, in order to test whether cookware is compatible, a magnet can be used to confirm whether the material is ferrous; if the magnet sticks to the cookware, then it can be used for induction cooking.
The elements underneath the cooking surface produce the electromagnetic field causing electrons within the ferrous metal cookware to start vibrating and producing heat.
Placing a ferrous metal pot or pan on the surface of the induction cooker activates the element and in turn, this goes on to cause the contents of the cookware to heat up.
Generally, a high 24 kHz frequency alternating electric current is used for induction cooking. The field produced in the cookware is known as an eddy current; these go on to produce heat as a result of the resistive heating process (also known as Joule heating). The pot or pan then goes on to heat its contents through the process of heat conduction.
The degree of heat, or thermal energy, that can be converted in the cookware from the resistance to the magnetic field, depends upon the amount of surface resistance the metallic material is capable of. With the same frequency of AC electric current, a metal surface with a greater resistance will produce a greater degree of heat.
For this reason, cookware made up of only copper, aluminum or Pyrex won’t work for induction cooking; this is due to the decreased resistance to the flow of current within the metal layer. Effectively, less heat is produced within the copper or aluminum, and consequently your food won’t be cooked.
Because all of the thermal energy is directly converted from the magnetic field induction, the amount of heat generated in the cookware can be finely manipulated by simply controlling the strength of the magnetic field. Any changes made to the strength of the magnetic field are therefore able to instantaneously alter the degree of heat inside the cooking vessel.
What this means is that induction cooking is much safer than other forms of heating, the cooker can be incredibly quickly turned off. Additionally, because the cooker’s surface is itself only heated by the cookware in which the heat is generated, the induction stove’s exterior generally cannot reach a dangerous temperature.
An induction cooker’s control system can also turn off the magnetic element if no ferrous pot is present, being able to detect the presence of cookware by checking the degree of power delivered.
Cookware has to fit the size of the element. If a pot or pan is not large enough, the induction cooker’s safety sensor won’t be triggered and therefore, the element won’t be activated. As a result, the cooktop does not start heating a ferrous metal unless it spans the diameter of the cooking surface. This is an important safety mechanism.
By directly heating the pot or pan, induction cooking is a great deal more efficient than traditional electric or gas cooking methods. Whereas with electric heating elements and flames a lot of energy is wasted, with induction cooking, these inefficiencies through losses by convection and radiation are minimized. Consequently, less heat is lost through heating up your kitchen when really it is the food which needs to be heated up.
Using non-ferrous cookware
If you really want to use pots and pans that aren’t made of a magnetic ferrous metal, an induction disk, made up of a ferromagnetic metal such as stainless steel or cast iron, can be placed on the induction surface. Therefore, the heat will be generated inside this disk and can be transferred by conduction through to any other material such as aluminum, copper or Pyrex.
Generally, this isn’t recommended because the efficiency advantages of induction cooking are consequently made redundant.
One common misconception is that induction cooking materials have to be able to conduct electricity. Understandably, it is easy to assume that induction relies on electrical conductivity, but in actual fact it is the contents of iron within the cookware material, and its ferrous properties, that makes the material suitable for induction cooking purposes.