College Physics III – Thermodynamics, Electricity, and Magnetism
Definition
An induced magnetic field is a magnetic field that is generated by the movement of an electric charge or by a changing electric field. This phenomenon is described by Faraday's law of electromagnetic induction, which states that a changing magnetic field can induce an electromotive force (EMF) in a conductor, leading to the creation of an induced magnetic field.
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The strength of the induced magnetic field is proportional to the rate of change of the original magnetic field, as described by Faraday's law.
Induced magnetic fields can create opposing forces that oppose the change in the original magnetic field, as described by Lenz's law.
Eddy currents, which are circular electric currents induced in a conductive material, can create their own induced magnetic fields that oppose the change in the original magnetic field.
Induced magnetic fields can be used in various applications, such as transformers, electric generators, and induction motors.
The direction of the induced magnetic field is determined by the direction of the changing magnetic field and the relative motion between the conductor and the magnetic field, as described by Lenz's law.
Review Questions
Explain how an induced magnetic field is created and how it relates to Faraday's law.
An induced magnetic field is created when a changing magnetic field induces an electromotive force (EMF) in a conductor, as described by Faraday's law. Faraday's law states that the induced EMF is proportional to the rate of change of the magnetic field. This induced EMF can then create a current in the conductor, which in turn generates its own magnetic field, known as the induced magnetic field. The strength of the induced magnetic field is directly related to the rate of change of the original magnetic field.
Describe the relationship between induced magnetic fields and Lenz's law.
Lenz's law states that the direction of the induced magnetic field is such that it opposes the change in the original magnetic field. This means that the induced magnetic field will create a force that opposes the change in the original field. For example, if the original magnetic field is increasing, the induced magnetic field will create a force that opposes this increase. Conversely, if the original magnetic field is decreasing, the induced magnetic field will create a force that opposes this decrease. This relationship between the induced magnetic field and the original magnetic field is a fundamental principle in the understanding of electromagnetic induction.
Analyze the role of eddy currents in the creation of induced magnetic fields and their practical applications.
Eddy currents are circular electric currents that are induced in a conductive material when it is exposed to a changing magnetic field. These eddy currents can create their own induced magnetic fields that oppose the change in the original magnetic field, as described by Lenz's law. The induced magnetic fields created by eddy currents can have both positive and negative practical applications. On the one hand, they can be used in devices like transformers, electric generators, and induction motors to convert energy between electrical and mechanical forms. On the other hand, they can also lead to energy losses and unwanted heating in certain applications, such as in the cores of electrical machines. Understanding the role of eddy currents and their induced magnetic fields is crucial for the design and optimization of various electromagnetic devices and systems.
The process in which a changing magnetic field induces an electric current in a conductor, as described by Faraday's law.
Faraday's Law: A law that describes the relationship between a changing magnetic field and the induced electromotive force (EMF) in a conductor, which can lead to the creation of an induced magnetic field.
Circular electric currents that are induced in a conductive material when it is exposed to a changing magnetic field, which can create an opposing induced magnetic field.