Wikibooks: A-level Physics/Forces, Fields and Energy/Electromagnetic induction

• Format: Book
• Language: English
• Subjects: North Pole; Faraday
• Online Access: https://en.wikibooks.org/wiki/A-level_Physics/Forces,_Fields_and_Energy/Electromagnetic_induction

We have already investigated that passing a current through a wire in a magnetic field causes a force to be exerted on it. The opposite is also true and when a force is exerted on a wire a current is induced in the wire. This completely revolutionised the world because it meant that electricity could now be cheaper to produce. =Inducing an EMF.= When a conductor is moved through a magnetic field an EMF is generated and the interaction of the magnetic field produced by the conductor with the magnetic field that was present cause deflection. =Faraday s Law= Michael Faraday state in his law that The magnitude of the electromotive force(EMF) generated is proportional to the rate of change of magnetic field Magnetic Flux density is a measure of the strength of a magnetic field and is essentially how dense the field lines of a magnetic field are within a given height. =Reversing the motor effect B/A= =Magnetic flux= =Direction of induced current= Direction of induced current is according to the Lenz s law which states that current in a coil is induced such that it always opposes the change producing it. For example if we bring north pole of a magnet towards a neutral coil with some velocity the current is induced in a way that it opposes the north pole or simply north pole is induced at the side where north pole is brought near which will result in the flow of current in the coil. If we assume a coil placed on a horizontal air space and bring north pole towards it from upper side and then we see coil from upper side the current induced is in anti clockwise direction. =Calculating the induced EMF= Faraday s law states Induced EMF is equal to the rate of change of magnetic flux. Magnetic flux = Magnetic field strength x Area = BA. Rate of change implies we consider the variable with respect to time (in seconds) Therefore.Induced EMF = (change in Magnetic Flux Density x Area)/change in Time. OR EMF = BA/t If we are doing it with a coil the area becomes the area of one coil multiplied by the number of coils A = πr 2 n ...