b. electrons drift slowly toward the positive end of the wire
Explanation:
Motion of electrons constitutes current. According to Ohm's law, the current in the wire is directly proportional to the potential difference across the two ends of the wire.
I ∝ V
⇒V = I R
When potential difference is put, the electrons towards the positive end. Thus, option b is correct.
As the potential difference is applied accros a wire, the electron drifts slowly towards the positive end of the wire as the electrons are negatively charged so they attract towards the positive end.
