Why is the magnetic field stronger at this specific point?

AI Thread Summary
The induced EMF in a rotating rod is greater at point R than at point P due to the larger area of the enclosed circuit, not because the magnetic field strength is different. The magnetic field remains constant throughout the rotation. The EMF can be calculated using the formula ε = ∮(v × B) · dl, where v represents the velocity of charges in the circuit. As the distance from the origin increases, both the velocity of the charges and the length of the integration path increase, leading to a higher EMF. Understanding these factors clarifies why the EMF varies at different points along the rod.
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A rod (shown in the picture on the link) rotates around the point O in a magnetic field. It is said for sure that the induced EMF in the rod is larger at point R compared to point P. Why's that?

The picture: http://img58.imageshack.us/my.php?image=physicskx4.png
 
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The EMF is larger because the area of the enclosed circuit is larger. The magnetic field is NOT larger, it is constant.
 
Nick89 said:
The EMF is larger because the area of the enclosed circuit is larger. The magnetic field is NOT larger, it is constant.

Oh I meant the EMF of course. But can you please explain your answer more thoroughly I don't fully understand the situation.
 
The EMF is given by:
\epsilon = \oint \left( \textbf{v} \times \textbf{B}\right) \cdot d\textbf{l}
Here, B is the magnetic field, dl is a small segment of a circuit, and v is the velocity of a charge in that circuit.

If you think of the electrons in the rotating rod as charges going around in a circular circuit, then you can easily see why the EMF is larger when you get further from the origin.
First of all, the velocity v is larger, secondly the path of integration (the length of the loop) is larger.
 
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