Ampere’s Law Concept Questions:
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Ampere’s Law Concept Questions:. A coaxial cable is shown at right. This type of cable has a central cable that carries the forward current and an outer conducting sheath that carries the return current. Outer conductor carrying return current I. Inner conductor carrying forward current I. X.
Ampere’s Law Concept Questions:
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Ampere’s Law Concept Questions: A coaxial cable is shown at right. This type of cable has a central cable that carries the forward current and an outer conducting sheath that carries the return current. Outer conductor carrying return current I Inner conductor carrying forward current I X Question: What is the magnetic field outside the wire? A) C) B) D) 0
Electromagnetic Induction Demonstration 1: The north pole of a magnet is plunged into a solenoid coil. Observation of effect on ammeter needle: Demonstration 2: The North pole of the magnet is held at rest in the coil. Demonstration 3: The North pole of the magnet is pulled OUT of the coil. Demonstration 4: The South pole of the magnet is plunged into the coil. Demonstration 5: The South pole of the magnet is moved slowly into the coil and then moved rapidly into the coil. Summary of observations?
Michael Faraday- 1831 Faraday’s Law of Electromagnetic Induction A changing magnetic field in the presence of a conductor will induce charge to flow in a conductor. ● basis of electric generating turbines wind water steam Generates current in conducting coils Rotates magnets ● Complement to Oersted’s Law of Electromagnetism Oersted Current (moving charge) Magnetic Field Faraday
Lenz’s Law-1835 The induced electric current produces its own magnetic field which OPPOSES the changing magnetic field. ● based on Conservation of Energy ● electric potential energy INCREASES as charge separated ● balanced by a DECREASE in kinetic energy of the changing magnetic field ● loss of kinetic energy felt as an OPPOSITION to the changing field
Demonstrations of Lenz’s Law Ex. 2: Pull a N pole of a bar magnet out of a coil What is the direction of the induced current? Ex. 1: Plunge a N pole of a bar magnet into a coil What is the direction of the induced current? Induced N pole Induced S pole N S
Ex. 3: Compare the rate of fall of a steel plug and a magnet in a copper pipe. Observations? The magnet falls much SLOWER than the metal plug. Reason: The changing magnetic field induces a current loop called an EDDY CURRENT in the pipe that opposes the changing field!