What effect does applying positive voltage to the P end and negative to the N end of a germanium diode have?

Applying a positive voltage to the P (anode) end and a negative voltage to the N (cathode) end of a germanium diode creates a forward bias condition. In semiconductor diodes, forward bias occurs when the potential on the anode is higher than that on the cathode, allowing current to flow through the diode.

In the case of germanium diodes, they typically require a lower forward voltage (around 0.3 volts) compared to silicon diodes, which usually require about 0.7 volts. When forward biased, the charge carriers (holes in the P-type material and electrons in the N-type material) are pushed toward the junction, thereby reducing the barrier to current flow and allowing the electrons and holes to recombine. This process results in current flowing from the anode to the cathode, thus enabling the diode to conduct electricity.

The other choices do not apply in this scenario: reverse bias occurs when the P side is negative relative to the N side, which stops current flow; opening the circuit suggests no current flow, which is contrary to forward bias; and a short circuit entails a low-resistance connection that allows excessive current to flow, which is not the case in a properly biased diode.