INDUCED ELECTROMOTIVE FORCE group 4 1.Firdiana Sanjaya Ana Alina

Linking electricity and magnetism

From these observations, we conclude that the loop detects that the magnet is moving relative to it and we relate this detection to a change in magnetic field. Thus, it seems that a relationship exists between current and changing magnetic field.

Linking electricity and magnetism The conclution from all these observations is that a changing magnetic field will produce a voltage in a coil, causing a current to flow. To be completely accurate, if the magnetic flux through a coil is changed, a voltage will be produced. This voltage is known as the induced emf.

Linking electricity and magnetism The magnetic flux is a measure of the number of magnetic field lines passing through an area. If a loop of wire with an area A is in a magnetic field B, the magnetic flux is given by:

Linking electricity and magnetism If the flux changes, an emf will be induced. There are therefore three ways an emf can be induced in a loop: Change the magnetic field Change the area of the loop Change the angle between the field and the loop

Faraday's law of induction an emf can be induced in a coil if the magnetic flux through the coil is changed. It also makes a difference how fast the change is; a quick change induces more emf than a gradual change. This is summarized in Faraday's law of induction. The induced emf in a coil of N loops produced by a change in flux in a certain time interval is given by:

Recalling that the flux through a loop of area A given by Faraday’s law can be written

An example Consider a flat square coil with N = 5 loops. The coil is 20 cm on each side, and has a magnetic field of 0.3 T passing through it. The plane of the coil is perpendicular to the magnetic field: the field points out of the page.

(a) If nothing is changed, what is the induced emf? There is only an induced emf when the magnetic flux changes, and while the change is taking place. If nothing changes, the induced emf is zero. (a) If nothing is changed, what is the induced emf? There is only an induced emf when the magnetic flux changes, and while the change is taking place. If nothing changes, the induced emf is zero.

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