(no subject)
ALL FOR DANA!! hope it helps ya hun!! =)
Charles Sturt University, New HSC Online “9.3 Motors and generators: 2. The generator”, October 2004 http://hsc.csu.edu.au/physics/core/motors/2606/PHY932net.html (25th of February, 2005)
Gather, analyse and present information to explain how induction is used in cook tops in electric ranges
Each cooking area on the ceramic induction cook top has one or more coils wound on ferromagnetic material under it. A high frequency alternating current is passed through these coils producing a fluctuating magnetic field. When a ferromagnetic-based pan is placed over the coils, eddy currents are induced in the base because of the fluctuating magnetic field. The eddy currents are trapped within the pan because the ceramic cook top is an electrical insulator.
The pan must be made from a metal that has a high internal resistance to this induced AC current. The resistance to the rapidly oscillating currents within the pan results in heat being produced directly in the base of the pan. That heat is dissipated to the food in the pan and does the cooking. The ceramic cook top itself is not heated other than by heat lost from the pan. The induction cook top works best when used with pans made of ferromagnetic metals such as stainless steel and cast iron.
Gather secondary information to identify how eddy currents have been utilised in electromagnetic braking
Eddy currents are used for electromagnetic braking in many free-fall amusement park rides. A copper plate attached to the ride capsule passes between fixed strong magnets near the bottom of the ride, inducing eddy currents and associated magnetic poles in the copper plate. Each fixed magnet in turn induces a like pole as the plate approaches and an opposite pole as the plate leaves. The combined effect of interaction between the permanent and the induced fields slows the ride down smoothly because the strength of the eddy currents in the plate is directly proportional to the speed of the plate moving between the poles. As the ride slows the braking force is reduced.
Some trains use electromagnets close to the metal rails to induce eddy currents in the rails. These eddy currents produce magnetic fields in the rails, a like pole ahead of each electromagnet and an opposite pole behind it. The interaction between the magnetic fields opposes the forward motion of the electromagnets and the train to which they are attached. Because the strength of the induced eddy currents is proportional to the speed of the train, the braking force is reduced as the train slows, resulting in a smooth stop.
Triple beam balances commonly used in school laboratories have an aluminium plate fixed to the end of the beam. As the beam swings, the plate passes through the field of a permanent horseshoe magnet. Eddy currents are induced in the plate, setting up magnetic fields and damping the motion of the balance.
Boston University, PY106 - Elementary Physics II “Applications of Electromagnetic Induction”, 22nd of July, 1999 http://physics.bu.edu/~duffy/PY106/Electricgenerators.html (25th February 2005)
Applications of electromagnetic induction
Electromagnetic induction is an incredibly useful phenomenon with a wide variety of applications. Induction is used in power generation and power transmission, and it's worth taking a look at how that's done. There are other effects with some interesting applications to consider, too, such as eddy currents.
Eddy currents
An eddy current is a swirling current set up in a conductor in response to a changing magnetic field. By Lenz¹s law, the current swirls in such a way as to create a magnetic field opposing the change; to do this in a conductor, electrons swirl in a plane perpendicular to the magnetic field.
Because of the tendency of eddy currents to oppose, eddy currents cause energy to be lost. More accurately, eddy currents transform more useful forms of energy, such as kinetic energy, into heat, which is generally much less useful. In many applications the loss of useful energy is not particularly desirable, but there are some practical applications. One is in the brakes of some trains. During braking, the metal wheels are exposed to a magnetic field from an electromagnet, generating eddy currents in the wheels. The magnetic interaction between the applied field and the eddy currents acts to slow the wheels down. The faster the wheels are spinning, the stronger the effect, meaning that as the train slows the braking force is reduced, producing a smooth stopping motion.
Brandt, Kitchen Appliances: Tomorrow’s Technology for Today “Induction Cooking”, December 2004 http://www.cookpower.com/ (25th February 2005)
Brandt presents its revolutionary cooking method. Induction cooking is the major culinary breakthrough of recent years. Never before have ease of use, energy efficiency and safety come together in a single product as in Brandt induction hobs. Every Brandt hob has a microprocessor which ensures that heat is generated only when suitable cookware is used - and then, as if by magic, only the cookware heats up. The cooking surface itself stays cool, making induction cooking safer and faster than gas or electric hobs and providing you with total control.
Safety
• The cool hob surface and the automatic temperature cut-out feature reduces the risk of burns when a plate is left on accidentally or when a pot boils dry. Spilt fat or oil - will not ignite.
Control
• Now you have more immediate and total control over all aspects of cooking than ever before, whether you have use electric, gas or halogen hobs.
Speed
• As the cookware itself becomes the source of heat for cooking, you enjoy very rapid heating and instant temperature adjustment at the touch of a finger.
Economy
• An energy saving of 60% is achievable, owing to reduced cooking times and less wastage of heat, resulting in lower power bills.
Easy-Clean
• The cool hob temperature ensures that any spillages do not burn onto the ceramic surface and can easily be wiped off.
Simplicity
• Accurate touch-tronic controls as well as state-of-the-art heat sensors represent the ultimate in simplicity and take the guesswork out of cooking.
Power Sharing
• All Brandt induction hobs feature a unique power sharing facility which allows you to allocate available power for super-fast heating.
Climate
• As all the heat is centred in the cookware itself, no extra heat enters the atmosphere, keeping your kitchen cooler while cooking.