6: Electromagnetic Induction
- Page ID
- 48150
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In our development thus far, we have found the electric and magnetic fields to be uncoupled. A net charge generates an electric field while a current is the source of a magnetic field. In 1831 Michael Faraday experimentally discovered that a time varying magnetic flux through a conducting loop also generated a voltage and thus an electric field, proving that electric and magnetic fields are coupled.
- 6.1: Faraday's Law of Induction
- Faraday's original experiments consisted of a conducting loop through which he could impose a dc current via a switch. Another short circuited loop with no source attached was nearby, as shown in Figure 6-1.
- 6.2: Faraday's Law for Moving Media
- Various alloys of iron having very high values of relative permeability are typically used in relays and machines to constrain the magnetic flux to mostly lie within the permeable material.
- 6.3: Energy Stored in the Magnetic Field
- If a point charge q travels with a velocity v through a region with electric field E and magnetic field B, it experiences the combined Coulomb-Lorentz force
- 6.4: The Energy Method for Forces
- If the current distribution is known, the magnetic field can be directly found from the Biot-Savart or Ampere's laws. However, when the magnetic field varies with time, the generated electric field within an Ohmic conductor induces further currents that also contribute to the magnetic field.
- 6.5: Energy Stored in The Magnetic Field
- The differential amount of work necessary to overcome the electric and magnetic forces on a charge q moving an incremental distance ds at velocity v is
- 6.6: The Energy Method for Forces
- In Section 6-5-1 we calculated the energy stored in a current-carrying loop by two methods. First we calculated the electric energy input to a loop with no mechanical work done.
Thumbnail: Animation showing operation of a brushed DC electric motor. (CC BY-SA 3.0; Abnormaal via Wikipedia)