When the current through the coil of an electromagnet reverses,the -a,direction of the magnetic field reverse b, direction of the magnetic field remains unchanged c, magnetic field expands d, magnetic field collapses?
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A changing magnetic field, such as a magnet moving through a conducting coil, generates an electric field (and therefore tends to drive a current in such a coil). This is known as Faraday's law and forms the basis of many electrical generators and electric motors.
Mathematically, Faraday's law is:
{\displaystyle {\mathcal {E}}=-{\frac {\mathrm {d} \Phi }{\mathrm {d} t}},}
where {\displaystyle \scriptstyle {\mathcal {E}}} is the electromotive force (or EMF, the voltage generated around a closed loop) and Φ is the magnetic flux—the product of the area times the magnetic field normal to that area. (This definition of magnetic flux is why B is often referred to as magnetic flux density.)[33]:210
The negative sign represents the fact that any current generated by a changing magnetic field in a coil produces a magnetic field that opposes the change in the magnetic field that induced it. This phenomenon is known as Lenz's law.
This integral formulation of Faraday's law can be converted[nb 15] into a differential form, which applies under slightly different conditions. This form is covered as one of Maxwell's equations below.
Mathematically, Faraday's law is:
{\displaystyle {\mathcal {E}}=-{\frac {\mathrm {d} \Phi }{\mathrm {d} t}},}
where {\displaystyle \scriptstyle {\mathcal {E}}} is the electromotive force (or EMF, the voltage generated around a closed loop) and Φ is the magnetic flux—the product of the area times the magnetic field normal to that area. (This definition of magnetic flux is why B is often referred to as magnetic flux density.)[33]:210
The negative sign represents the fact that any current generated by a changing magnetic field in a coil produces a magnetic field that opposes the change in the magnetic field that induced it. This phenomenon is known as Lenz's law.
This integral formulation of Faraday's law can be converted[nb 15] into a differential form, which applies under slightly different conditions. This form is covered as one of Maxwell's equations below.
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