Thermal stresses caused by uneven cooling can easily break glass cookware. Explain why Pyrex, a glass with a small coefficient of linear expansion, is less susceptible.
Electromagnetic Induction Goals • To examine experimental evidence that a changing magnetic field induces an emf • To learn how Faraday’s law relates the induced emf to the change in flux • To determine the direction of an induced emf • To calculate the emf induced by a moving conductor • To learn how a changing magnetic flux generates an electric field • To study the four fundamental equations that describe electricity and magnetism Introduction • How is a credit card reader related to magnetism • Energy conversion makes use of electromagnetic induction. • Faraday’s law and Lenz’s law tell us about induced currents. • Maxwell’s equations describe the behavior of electric and magnetic fields in any situation. Induced current • A changing magnetic flux causes an induced current. • The induced emf is the corresponding emf causing the current. Copyright © 2012 Pearson Education Inc. Magnetic flux through an area element • how to calculate the magnetic flux through an element of area. Copyright © 2012 Pearson Education Inc. Faraday’s law • The flux depends on the orientation of the surface with respect to the magnetic field. • Faraday’s law: The induced emf in a closed loop equals the negative of the time rate of change of magnetic flux through the loop, or = –d /dt. B Copyright © 2012 Pearson Education Inc. Emf and the current induced in a loop Copyright © 2012 Pearson Educati