Welcome to ‘Kagoo Explains’ - a series of short articles de-mystifying some of the confusing terminology used to describe tech. Today we’re looking at induction cooking - a super-fast, energy efficient heating method very different from standard gas or electric heating.
Despite all the technological advances of the modern age, cookers and hobs have remained largely unchanged when it comes to heating pots and pans - a gas burner or electrical element is heated to very hot temperatures, and a cooking pot is placed on top. The heat transfers from the hotter body (the cooker) to the cooler one (the pot) - this process is known as ‘thermal conduction’. While this is the standard heating method for hobs and cookers, it’s far from the only one - today we’ll be looking at a more modern method: induction cooking.
Induction cooking uses the principle of ‘electromagnetic induction’ to generate a large amount of heat in the material of the pan itself, rather than transferring heat from the burner to the pan. There are significant advantages to this method - it allows for extremely fast heating with far less energy wastage, and is far safer as well! The only major downside is that it requires certain materials to work - specifically ‘ferromagnetic metals’ such as cast iron or some forms of stainless steel. Therefore certain pans aren’t compatible with induction hobs - ceramic, glass and aluminium pots won’t heat at all.
Magnets: not just for fridge doors anymore
Before we get into the specifics of induction cooking, we have to understand the concept of electromagnetic induction itself. As the name suggests, induction uses both electricity and magnetism - two forces that are very closely linked. In 1931, Michael Faraday discovered two important concepts:
When a magnet is placed near a wire fed with electric current, the wire generates a magnetic field
When a wire is rotated through a magnetic field, an electric current would run through it
These two important discoveries are used together to create electromagnetic induction - a magnet is placed near a wire fed with a current, which generates a magnetic field that causes a current to appear in a second, nearby wire. Therefore using induction, electric current can be created without the need for any battery or physical connection - clever stuff indeed!
Induction is used for many purposes, including wireless charging - a wireless charging mat generates a small magnetic field when active, which induces a current into a compatible phone, charging up the battery.
If it keeps on raining, eddy’s gonna break...
So how does induction help our cooking? The basic principles are the same, but with one important difference - ‘eddy currents’. When the magnetic field of a conductor changes from positive to negative, it creates a small secondary current inside the conductor - this is called an eddy current. These currents then have their own magnetic fields, which can then intersect with the currents and fields already churning around inside the conductor. Effectively they are closed loops of current and - most importantly - they generate heat when flowing through an object with high resistance.
This is where the ferromagnetic metals such as cast iron come in. Cast iron is a very good conductor of electricity, but it is an extremely poor conductor of heat. This makes it perfect for induction, since it has a very high resistance for the eddy currents - the eddy currents generate heat inside the material of the pot, and the heat is ‘trapped’ by the poor conductivity of the metal. This is what allows induction cooking to heat up pots so effectively and efficiently - there is little heat loss, which means far less energy wastage and a more efficient cooker!
The physical makeup of an induction hob is very simple, and follows the concepts we’ve been talking about - the hob surface is made of glass or ceramic, and placed under it is a tight coil of copper wire with a current running through it. This is the electromagnet - when the pan is placed on top of the surface, it enters the magnetic field from the coil and bam - heating!
Crank that AC up!
However there is a problem: standard eddy currents are far too weak to generate enough useful heat. In order to power them up enough to make cooking work, there needs to be a very high rate of change in the current that first induces the eddys - therefore a very strong AC (alternating current) flow is needed. In order to achieve this, induction cookers and hobs transform the current before it arrives at the coil - the frequency (the number of times the current changes per second) is increased by 1,000 times!
The frequency of an alternating current affects how regularly the corresponding magnetic field changes from positive to negative. The power - and therefore the heating capability - of eddy currents grows with faster changes, so an increase of 1,000 means a *massive* boost to the heating capability
The end result is a barrage of super-powered eddy currents bouncing around the bottom of the cast iron pot with nowhere to go… therefore they give off tremendous amounts of heat, heating your pan to high temperatures very quickly!
Finally, one important benefit of induction we haven’t talked about - because the heat is being generated *inside* the pot, it means that the cooking surface itself stays cool - since no actual heat is being transferred, just magnetic fields. This means that induction heating is far safer - although you must still be careful, since the surface may heat up anyway from having the hot pan standing on it. Safety first!
So there you have it - hopefully you understand the magic of electromagnetic induction now! If it’s given you a hankering to do some cooking, check out Kagoo for a comprehensive list of the best induction cookers and best induction hobs! (LINKY)