8/26/2023 0 Comments Emf formula magnetic flux![]() When the magnet is motionless with respect to the coil, no current is induced in the coil, as in Figure 20.33. He found that current is induced only when the magnet moves with respect to the coil. A schematic of this experiment is shown in Figure 20.33. One experiment Faraday did to demonstrate magnetic induction was to move a bar magnet through a wire coil and measure the resulting electric current through the wire. Other devices that use magnetism to induce currents include pickup coils in electric guitars, transformers of every size, certain microphones, airport security gates, and damping mechanisms on sensitive chemical balances. The electric generator-found in everything from automobiles to bicycles to nuclear power plants-uses magnetism to generate electric current. “Madam,” he replied, “What good is a baby?” Today, currents induced by magnetic fields are essential to our technological society. When Faraday discovered what is now called Faraday’s law of induction, Queen Victoria asked him what possible use was electricity. The basic process of generating currents with magnetic fields is called induction this process is also called magnetic induction to distinguish it from charging by induction, which uses the electrostatic Coulomb force. In 1831, some 12 years after the discovery that an electric current generates a magnetic field, English scientist Michael Faraday (1791–1862) and American scientist Joseph Henry (1797–1878) independently demonstrated that magnetic fields can produce currents. If nature is symmetrical, then perhaps a magnetic field can create a current. The coil’s rotation causes a change in the magnetic flux of the magnetic field of the coil, so the EMF keeps inducing in the coil.In the preceding section, we learned that a current creates a magnetic field. The coil’s rotational axis is kept normal to the direction of the magnetic field. There is a change in the magnetic flux of a magnetic field when the coil rotates, and hence, it induces an emf. ![]() The principle of electric generators is that the EMF is induced by rotating a coil in a magnetic field and changing magnetic flux. One of the important applications of electromagnetic induction is an electrical generator. Therefore, the general means by which we can change the magnetic flux through a coil are as follows:īy changing the magnitude of the magnetic field.īy changing the total area of the coil or the portion of that area by expanding the coil.īy changing the angle between the direction of the magnetic field and the plane of the coil.įleming’s right hand rule states that if we stretch our right hand thumb, the index finger, and a middle finger such that all three are mutually perpendicular to each other, the thumb represents the direction of motion of conductor, the index finger represents the direction of magnetic field, then the middle finger represents the direction of current induced.Įlectromagnetic induction through a change in magnetic flux is the principle behind the functioning of transformers, inductors, and many types of generators, electrical motors, and solenoids. ![]() The changes in flux Δ Φ \Delta \Phi Δ Φ and EMF are directly proportional.ĮMF is directly proportional to the number of turns in a coil, N.ĮMF is inversely proportional to the change in time, Δ t \Delta t Δ t The EMF induced hence depends on following factors: The negative sign indicates that the emf induced in the coil acts to oppose any change in the magnetic flux The EMF is equal to the negative rate of flux change. Φ B = B ⃗ ⋅ A ⃗ = B A cos θ E M F = Δ t − N Δ Φ The magnetic flux represents the total magnetic lines of force passing through a given area.įlux associated with a plain coil area A, having N turns in a uniform magnetic field B, is given by ![]() The magnetic flux that occurred in the coil is proportional to the amount of current flowing in the coil. The static magnetic field around the coil acts as a bar magnet, which has a distinct North Pole and South Pole. When current passes through a long coil or solenoid, a magnetizing force and a magnetic field gets developed around it.
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