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