Induction cooktops by Chris Woodford. Last updated: April 20, Cooking is one of the oldest of technologies—and for obvious reasons: humans would never have survived let alone thrived without perfecting the art of feeding themselves. The basic idea of cookery—heating food to kill bacteria and make something nutritious and tasty—is fairly prehistoric: "food plus fire equals cooked food" is roughly how it goes.

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Induction cooktops by Chris Woodford. Last updated: April 20, Cooking is one of the oldest of technologies—and for obvious reasons: humans would never have survived let alone thrived without perfecting the art of feeding themselves. The basic idea of cookery—heating food to kill bacteria and make something nutritious and tasty—is fairly prehistoric: "food plus fire equals cooked food" is roughly how it goes.

In the 20th century alone, ingenious inventors came up with two brand new forms of cooking. One, the microwave oven , uses high-energy radio waves to heat food quickly and efficiently in a fraction of the time you need with a conventional stove.

The other, induction cooking, uses electromagnetism to turn cooking pans into cookers creating heat energy inside the pan itself, instead of firing it in from outside , which cooks food more quickly and safely with less energy.

Everyone knows about microwaves these days, but induction cookers are much less well understood. Photo: Induction cooktops, made from easy-to-clean toughened glass, look much the same as other ceramic cooktops.

What is induction? Before you can understand induction cooking, you need to understand induction. And the first thing you need to know is that "induction" is a shortened way of saying "electromagnetic induction.

Electromagnetism Photo: James Clerk Maxwell, who described the science of electromagnetism in four equations. Public domain photo by courtesy of Wikimedia Commons. A handful of brilliant European scientists figured out the science of electromagnetism—the mysterious relationship between electricity and magnetism—in a period of roughly 40 years spanning the middle of the 19th century. Their findings have proved to be among the most important discoveries ever made: scientists had known about electricity since ancient times, but understanding the science and technology of electromagnetism made it possible to power the world with electricity for the first time.

It all started in A Danish physicist named Hans Christian Oersted found that when a fluctuating electric current flows down a wire, it creates an invisible pattern of magnetism all around it a magnetic field, in other words.

So far, the emerging science of electromagnetism was completely theoretical: very interesting, but not much use. Things took a much more practical twist when the brilliant English physicist and chemist Michael Faraday figured out how he could use electricity and magnetism to develop a very primitive electric motor , also in He placed a magnet near a piece of wire into which he fed an electric current.

As the current flowed through the wire, it generated a magnetic field around it in the way Oersted had found , pushing itself away from the magnetic field that the permanent magnet generated. Other inventors notably Englishman William Sturgeon and American Joseph Henry went on to develop practical electric motors, while Faraday continued to experiment with the science.

In , he pulled off the opposite trick: he showed how rotating a coil of wire through a magnetic field would make an electric current flow through it—inventing the electricity generator that would soon in the hands of pioneers such as Thomas Edison bring electric power to the world.

The science of electromagnetism how electricity can make magnetism and vice-versa was finally nailed down by Scottish physicist James Clerk Maxwell in the s. Maxwell summarized everything that was then known about electricity and magnetism in four beautifully simple, crystal clear, mathematical formulas. Read more in James C. When you hear someone talking about induction, or something that uses induction, all it means is that magnetism is being used to generate electricity.

A common use for induction is in electric toothbrushes , which have one or two rechargeable batteries packed inside. The trouble with electric toothbrushes is that they get wet, so they need to have completely sealed plastic cases to keep their mechanisms safe and dry.

A conventional charger socket would be an open invitation to water as well. When your toothbrush battery runs flat, you sit it on a little plastic charger unit to recharge it. Although there is no direct electrical connection between the toothbrush and the charger both are made of plastic , electromagnetic energy flows from the charger into the toothbrush battery by induction, straight through the plastic that separates them: a coil of wire in the charger produces a magnetic field that induces an electrical current in a similar coil in the base of the toothbrush.

You can find out more and see some diagrams of exactly how it all works in our main article on induction chargers. Photos: Electric toothbrushes charge by induction: electromagnetic induction allows energy to flow from the white charger to the battery in the dark blue brush even though there is no direct electrical connection between them. How does an induction cooktop work? An induction cooktop a cooktop is called a "hob" in European countries is simply an electromagnet you can cook with.

When you turn on the power, you make a current flow through the coil and it produces a magnetic field all around it and most importantly directly above it.

So you have to use an alternating current one that keeps reversing direction to make a fluctuating magnetic field that will, indirectly, produce heat. It does not generate heat directly. Now this is not quite the same as the electric current that flows through a wire, carrying electrical energy in a straight line from say a battery to a flashlight bulb.

So the metal pan gets hot and heats up whatever food is inside it, first by conduction it passes its heat energy directly to the food but also by convection liquid food rises and falls in the pan carrying heat with it. Read more about heat transfer in our main article about heat energy. When you turn on the power, an alternating current flows through the coil and produces an invisible, high-frequency, alternating magnetic field all around it.

You might be wondering why we need a high frequency. Although your home power supply alternates at about 50—60Hz 50—60 times per second , an induction cooktop boosts this by about — times typically to 20—40kHz. No less importantly, it prevents magnetic forces from shifting the pan around on the cooktop. Place a pan on the cooking zone and the magnetic field produced by the coil shown here with blue lines penetrates the iron inside it.

The magnetic field induces whirling electrical eddy currents inside the pan, turning into a heater shown here in orange. Heat from the pan flows directly into the food or water inside it by conduction. Advantages of induction cooktops Photo: Gas burners are easy to control, but waste energy by heating the surrounding air and the cooktop as well as the food in the pan.

If you can easily cook with an electric ring or a gas-powered stove, why use an induction cooktop at all? There are quite a few good reasons. Efficiency and speed A traditional cooker generates heat energy some distance from the cooking pot or pan and attempts to transport as much of that energy into the food as possible—with varying degrees of success.

The main reason is that a huge amount of the energy you produce on an open fire is radiated out into the atmosphere; great for ambience, but very slow and inefficient. With induction cooking, the heat is produced in the pan, not the cooktop, and much more of the energy goes into the food. Induction cooking also gets energy to the food more quickly, because pans that get hotter faster cook faster. Convenience, control, and safety Induction cookers are usually built into ceramic or glass cooktops similar to halogen cooktops , which are very easy to keep clean with just a quick wipe.

The magnetic fields they produce make heat appear in the pan almost instantly—and they can make it disappear instantly too. You can turn the heat up or down with as much speed and control as a gas cooker unlike a traditional electric cooktop, which takes some time to heat up or cool down. On the other hand, induction cooktops are easy to switch on or off automatically, so some feature built-in timers, built-in temperature sensors, and even remote control from simple smartphone apps.

Heat appears only when the cooking pan is in place—and the cooktop itself can never get any hotter than the pan sitting on top of it. Induction cookers built into ceramic cooktops are only a couple of inches thick so they can be fitted at any height good for disabled people in wheelchairs who might want a low-level kitchen. Photo: Ceramic cooktops are strong, durable, and easy to wipe clean in seconds burned-on food can be gently and carefully removed with a shallow blade.

Less pollution Combustion-type cooking natural gas flames or even, in developing countries, open fires makes significant amounts of indoor air pollution. Gas stoves, for example, generate surprising amounts of nitrogen oxides , gases more commonly associated with diesel engines and outdoor smog. Another drawback is that induction cooking only works properly with cooking pans containing iron —the only metal that efficiently produces electrical eddy currents and heat from magnetic fields.

Indeed, some people even see it as an opportunity to upgrade. If you are going to replace your cookware, you could investigate "cool-touch" pots and pans made specifically for induction. Some have insulated outer bodies made from ceramics or heatproof plastics that stay relatively cool to the touch, with lumps of stainless steel or iron embedded in them to pick up the magnetic field from the cooktop and turn it into heat.

Some have built-in temperature sensors that help the cooktop to regulate the power it needs to supply, which also enables automatic, remote control from things like smartphone apps.

Artwork: Some induction cookers use smart pans with built-in sensors. The cooktop picks up the radio signal 7 and raises or lowers its power as necessary. Two other minor issues worth noting are that induction cooktops can produce a small amount of noise from built-in cooling fans and radio-frequency interference that might pose a very small risk for people wearing heart pacemakers no greater than the risk posed by other everyday electrical equipment. Should you buy an induction cooktop?

If you like the speed and control of gas, but prefer the wipe-clean convenience of a ceramic cooktop, and the relatively high initial purchase cost is not an issue, induction cooking might be worth considering.

Check your existing cookware before you buy; if you have to purchase an entire new set of quality pots and pans, that could add significantly to the outlay of switching to induction cooking. Sponsored links.

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Induction cooking

Cooking properties[ edit ] An induction cooking surface boiling water through several layers of newsprint. The paper is undamaged since heat is produced only in the bottom of the pot Power and control[ edit ] Induction cooking provides fast heating, improved thermal efficiency , and more consistent heating than cooking by thermal conduction. Induction cooking is generally digitally controlled which provides precise control of the power and cooking temperature. This makes it possible to boil a pot rapidly, and then keep a pot just simmering. Safety[ edit ] The unit can detect whether cookware is present by monitoring power delivered. As with other electric ceramic cooking surfaces, a maximum pan size may be specified by the manufacturer, and a minimum size is also stated.


Induction cooktops


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