HR30_post - Third midterm exam this Saturday, 11/12/2011 at...

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Unformatted text preview: Third midterm exam this Saturday, 11/12/2011 at 8:00 10:00 AM Test 2 covers material of chapters 27, 28 and 29 Room assignment, last name, first letter A R: NSC 225 S Z: NSC 201 Dr. Petrous section in Knox 20 1 Please bring with you the following items: c 2 pens c 1 calculator (make sure batteries have decent EMF) c 3 pages of 8.5 11 sheet with equations; will be handed with your test c Your student ID Students eligible for academic adjustments, please contact the Office of Accessibility Resources to schedule exam, either on Friday/11 th , Monday/14 th , or Tuesday/15 th at the latest Chapter 30 Induction and Inductance Will study the following topics Faradays law of induction Lenzs law Electric field induced by a changing magnetic field troduce the notion of ductance nd utual 2 Introduce the notion of inductance and mutual inductance How the current changes in RL circuits Calculate the energy stored in a magnetic field We know that an electric current produces magnetic field in a nearby space It turns out that the reverse can also happen: a magnetic eld can produce an electric field that can drive a current Magnetic Field Can Produce an Electric Current 3 field can produce an electric field that can drive a current This link between a magnetic field and the electric field it induces is called Faradays law of induction In series of experiments, Michael Faraday in England and Joseph Henry in the USA were able to generate electric current without the use of batteries We will discuss experiments similar to the ones that led Faraday to formulate Faradays Law of Induction Induction Experiment 4 The shown circuit consists of a wire loop connected to an ammeter. There is no emf in the circuit so there is no current If we move the bar magnet toward the loop, the ammeter will register a current in the loop The current disappears when the magnet stops moving If we move the magnet away, the ammeter will again register a current which now has the opposite direction If we experiment with the device for a while, we will be able to conclude the following: A current appears only if there is relative motion between the loop and the magnet ; the current disappears when the relative motion between them ceases Fast motion produces greater current Induction Experiment (contd) 5 The current produced in the loop is called an induced current The work done per unit charge to produce the induced current is called an induced emf This process of producing the current and emf is called induction If moving the magnets north pole toward the loop causes a current in one direction , then moving the north pole away causes current in opposite direction . Moving the south pole toward or away from the loop also causes currents, but in the reversed directions Loop 1 Loop 2 A scheme of an experiment with two nearby conducting loops is shown in Fig.nearby conducting loops is shown in Fig....
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HR30_post - Third midterm exam this Saturday, 11/12/2011 at...

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