how large is magnitude of the earths magnetic field and it does it induce any emf anywhere due to changing magnetic lines of force?

Asked by Gaurav Avhad | 12th Mar, 2011, 03:26: AM

Expert Answer:

Dear student,
 
Earth's magnetic field = 0.00005 Tesla
 

Motional emf

Let's say you have a metal rod, and decide to connect that to your galvanometer. If the rod is stationary in a magnetic field, nothing happens. If you move the rod through the field, however, an emf is induced between the ends of the rod causing current to flow. This is because when you move the metal rod through the field, you are moving all the electrons in the rod. These moving charges are deflected by the field toward one end of the rod, creating a potential difference. This is known as motional emf. Motional emf can even be measured on airplanes. As the plane flies through the Earth's magnetic field, an emf is induced between the wingtips.

Motional emf is largest when the direction of motion of the piece of metal is perpendicular to the rod and perpendicular to the magnetic field. When this is true, the motional emf is proportional to the speed of the rod, the length (L) of the rod, and the magnetic field:

If the metal rod is part of a complete circuit, the induced emf will cause a current to flow. Because it's in a magnetic field, the rod experiences a force because of the interaction between the field and the current. This force always acts to oppose the motion of the rod.

Hope this helps.
Team
Topperlearning.com

Answered by  | 12th Mar, 2011, 12:45: PM

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