I've been reading about the photoelectric effect for my modern physics class, and I was confused about how Ohm's law works in relation to it. Let's say we have a photoelectric apparatus that simply generates some current and then applies a stopping potential $V$ to bring the current to zero. If we increase the intensity, this increases the current. However, then $V = IR$, and resistance remains the same, so shouldn't voltage increase? This is against the fact that intensity and stopping potential are independent, so does this mean that Ohm's law just fails in this case? Thanks so much.
Answer
does this mean that Ohm's law just fails in this case
Ohm's law is not universal. The ideal resistor circuit element is defined by Ohm's law but not all circuit elements obey Ohm's law; Ohm's law only applies to ohmic devices.
Physical resistors and conductors approximately obey Ohm's law but, for example, semiconductor diodes, transistors, thyristors, solar cells, vacuum tubes, batteries, thermistors, etc. etc. etc. do not.
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