Electromagnetic Induction - ASKnLearn

Dunman High School (Senior High Physics Department)16.3.3 Induction stoveThe induction stove operates via eddy currents. Underthe cooking surface is an electromagnet that generatesan oscillating magnetic field. When a metal pan is puton the stove, the induced e.m.f. causes eddy currents toflow in the metal pan and the energy dissipated bythese currents is what heats the pan. The pan has to bemade of metal as it needs to be a conductor ofelectricity. The cooking surface is a non-conductor(usually ceramic) and eddy currents cannot flow in it,hence its temperature only rises to the extent that heatis conducted to it from the pan, i.e. the cooking surfaceis no hotter than the bottom of the pan.An induction stove has several advantages over gas, electric or halogen stoves:• Speed - Conductive heat transfer to the food is very direct, because the cookware isheated uniformly, and from within. Induction cooking is even faster than gas cooking.• Safety - There are no open flames, no heating elements. This reduces the chances of fire,and the cold stove top is also more child-safe.• Cleanliness - There are no burnt-in food residues, no messy grates. Just a smooth stovetop surface.• Efficiency - Since heat transfer is directly to the pan, this system is far more efficient thangas or electric cooking. Energy efficiency for induction cooking is around 90%; for electricand gas cooking this is around 65%, and 55% respectively.• Work Environment - Since less heat is lost to the surroundings, the workspace remainsrelatively cooler.16.3.4 Electric GuitarAn acoustic guitar depends on the acoustic resonance produced in the hollow body of theinstrument by the oscillations of strings. An electric guitar is, on the other hand, a solidinstrument, so there is no body resonance. Instead, the oscillations of the metal strings aresensed by electric “pickups” that send signals to an amplifier and a set of speakers.For each pickup, wire is coiled around a small magnet and this wire is connected to anamplifier. The magnetic field of the magnet produces a north an south pole in the section ofthe metal strong above the magnet. This section of string then has its own magnetic field.9646 Physics (2012)Topic 16: Electromagnetic Induction 16-10