Final answer:
The electric field in a rod runs from the positively charged end to the negatively charged end; hence, if point A is positive and point B is negative, the direction is from A to B.
Step-by-step explanation:
The direction of the electric field in the rod is from point A to point B if point A is positively charged and point B is negatively charged. This is because electric fields are defined as extending from positive charges towards negative charges. The electric field's direction can be determined using the principle that like charges repel and opposite charges attract. For instance, if you placed a positive test charge near point A, it would be repelled by the like charge at A and attracted to the unlike charge at B, indicating that the field lines must run from A to B. Therefore, in the scenario where point A is positive and point B is negative, the electric field would be directed from A to B.