# How Things Work: Magnetic Induction Cooktops

William Nicoll Feb 27, 2006

When making dinner, do your ingredients come in microwave-ready pouches? Do you prepare dinner in 30 seconds or less? If so, then stop reading. You’re not welcome here.

To the aspiring Food Network personalities out there, I’ve got the secret to great cooking: heat. While everyone enjoys salads and no-bake cookies, there is nothing quite like a warm, well-cooked meal. Things haven’t been the same since the extra-crispy rotisserie mammoth.

In the modern kitchen, the stove has become the tool of choice for our cooking needs. Stoves have a simple goal: convert a readily available form of energy into heat and transfer it to the food. Today’s most readily available sources of energy are electricity and natural gas. But how is that heat transferred?

You are probably familiar with a few forms of stove-top heat transfer. Gas stoves transfer heat through a simple, adjustable flame. Older electric stoves use “resistance heating,” where a metal coil heats up when a current passes through it. Fancy-schmancy households might even have a glass-ceramic stove-top, where infrared radiation is transmitted through a smooth cooking surface to provide heat.
Watch out, cookware: There is a new sheriff in town. His name is induction cooking.

Instead of conducting heat from the cooking surface to the cookware, induction heating utilizes electromagnetism to actually create heat within the cookware. The idea is not that new, actually. Since the early ’90s, the technology has gained increasing acceptance in Japan and Europe. American markets are just warming up to the idea.

Let’s turn up the heat.

If you have been (un)lucky enough to take an elementary physics course lately, you might know how magnetic induction works. If not, here’s the gritty: When an electrical conductor is placed in the presence of a changing magnetic field, electricity is produced in the conductor. This is the same phenomenon exploited in electrical motors and generators.

But how is this useful to cooking? In an induction stove, an electromagnet is placed underneath the cooking surface. When an alternating current runs through the electromagnet, a rapidly changing magnetic field is produced. An electric “eddy” current will be generated in large metal objects above this electromagnet, causing resistance heating. Unlike traditional electric stoves, this resistance heating takes place in the pot itself, not in a heating element underneath.

This type of heating has important implications for the cook. One of the most startling differences from traditional stoves is that the cooking surface doesn’t get hot! Because heat is only generated in the cookware, you can lay your hand right over the cooking surface and not burn yourself. This is a great advantage for children who don’t follow their parents’ advice.

Another advantage of induction cooking is its responsiveness. This is especially important for chefs, who demand more control over their cooking than the average college student. By varying the strength of the magnetic field, the heat generated in the pot is varied almost instantly. This responsiveness exceeds gas stoves and far exceeds traditional electric stoves.

Induction stoves are also excelling in their efficiency. Because heat is generated right at the surface of the cookware, less heat is lost to the environment. This equates to faster cooking time, cooler kitchens, and lower energy bills. Induction stoves average about 80 percent energy efficiency, compared to about 50 percent efficiency for conventional electric stoves and 30 percent efficiency for gas stoves. In real-life terms, this means the ability to boil water in half the time.

Unfortunately, induction stoves do have a big disadvantage: only ferrous (iron-containing) cookware can be used. This means that only cast-iron and steel pots and pans will work. Cookware made of aluminum, copper, ceramic, or glass will stay cold atop an induction stove. If a magnet can stick to your current cookware, it is “induction ready.” If not, get ready to stock up on stock pots.

As competition heats up in the induction stove market, look for prices to steadily fall. Current models still cost several thousand dollars, but they remain a niche item. If you are shopping for a new stove, don’t miss this hot new item!