College Physics III – Thermodynamics, Electricity, and Magnetism
Definition
Induced electromotive force (EMF) is the voltage or potential difference generated in a conductor when it experiences a changing magnetic field, as described by Faraday's law of electromagnetic induction. This induced voltage can drive an electric current in the conductor, powering various electrical devices and systems.
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The magnitude of the induced EMF is proportional to the rate of change of the magnetic flux through the conductor, as stated by Faraday's law.
The direction of the induced EMF is determined by Lenz's law, which states that the induced current will flow in a direction that opposes the change in the magnetic field.
Induced EMF can be used to generate electricity in devices such as generators, transformers, and induction motors.
The induced EMF is a consequence of the law of conservation of energy, as the induced current opposes the change in the magnetic field that caused it.
Induced EMF is a fundamental principle in the operation of many electrical devices and systems, including power transmission, wireless charging, and magnetic resonance imaging (MRI) technology.
Review Questions
Explain how the rate of change of the magnetic flux through a conductor affects the magnitude of the induced electromotive force (EMF).
According to Faraday's law, the magnitude of the induced EMF in a conductor is directly proportional to the rate of change of the magnetic flux through the conductor. This means that the faster the magnetic flux changes, the greater the induced EMF will be. This relationship is described by the equation: induced EMF = -N * (dΦ/dt), where N is the number of turns in the conductor, and dΦ/dt is the rate of change of the magnetic flux. The negative sign indicates that the induced EMF opposes the change in the magnetic field, as per Lenz's law.
Describe how the direction of the induced current in a conductor is determined by Lenz's law and how this relates to the principle of conservation of energy.
Lenz's law states that the direction of the induced current in a conductor is such that it opposes the change in the magnetic field that caused it. This is a consequence of the principle of conservation of energy, which requires that the induced current must generate a magnetic field that opposes the original change in the magnetic field. If the induced current flowed in the same direction as the change in the magnetic field, it would increase the original change, violating the conservation of energy. By opposing the change, the induced current helps to maintain the overall energy balance in the system.
Discuss the practical applications of induced electromotive force (EMF) and explain how it is utilized in various electrical devices and systems.
Induced EMF is a fundamental principle that is utilized in a wide range of electrical devices and systems. For example, generators use the principle of electromagnetic induction to convert mechanical energy into electrical energy by inducing an EMF in the generator's windings as they move through a magnetic field. Transformers rely on induced EMF to step up or step down voltages in power transmission systems. Induction motors use induced EMF to generate torque and rotation. Wireless charging devices, such as those used for smartphones, also rely on induced EMF to transfer power between the charging pad and the device. Additionally, induced EMF is a critical component in the operation of magnetic resonance imaging (MRI) machines, which use rapidly changing magnetic fields to generate images of the human body.
Related terms
Faraday's Law: Faraday's law of electromagnetic induction states that a changing magnetic field induces an electromotive force (EMF) in a nearby conductor, with the magnitude of the induced EMF proportional to the rate of change of the magnetic field.
Electromagnetic induction is the process by which a changing magnetic field creates an induced electric current in a nearby conductor, as described by Faraday's law.
Lenz's law states that the direction of the induced current in a conductor is such that it opposes the change in the magnetic field that caused it, in accordance with the principle of conservation of energy.