For convenience, I assume that the rod OP is horizontal.
1. Remember, current (positive charges) moves from high potential to low potential outside a battery, but it moves from low potential to high potential inside the battery.
2. An induced emf is a kind of battery. That is why it is called “induced emf”, not “induced potential difference”.
3. Right Hand Rule:
Motion –> downwards
B-field –> into the paper
So
current –> O to P
Then, P is at a higher potential.
4. Left Hand Rule:
Imagine you are a positive charge within the rod. The whole rod moves downloads. So you (the positive charge) move downloads.
current –> downloads
B-field –> into the paper
Therefore, you, as the positive charge, experience a force, pointing to the right. So the induced emf is pointing to the right.
Inside a battery, the direction of the emf is pointing from low potential to high potential. Thus, P is at a higher potential.
— Me@2014-03-19 01:54:04 PM
2014.04.29 Tuesday (c) All rights reserved by ACHK
Physics Town 