in the dark, is the current through an ldr higher or lower than in the light?

In the dark, the current through an LDR is lower than in the light, assuming the same voltage is applied.

How an LDR behaves

• An LDR (light-dependent resistor) has a very high resistance in the dark, often in the range of megaohms or more.

• In bright light, its resistance drops dramatically, sometimes to a few hundred ohms or less.

Because current III through a resistor at a given voltage VVV is given by Ohm’s law, I=VRI=\frac{V}{R}I=RV​, a higher resistance in the dark means a smaller current, and a lower resistance in the light means a larger current.

Quick mental picture

• Dark: Huge resistance → very little current flows.

• Light: Small resistance → current increases a lot.

So if you keep the circuit the same and only change the light level, the LDR carries less current in the dark and more current in the light.

In many automatic night-light circuits, the LDR is arranged in a divider so that when it goes high resistance in the dark, the voltage at another component (like a transistor or relay) rises and turns a lamp on, but the current through the LDR itself is still lower than in bright light.

Information gathered from public forums or data available on the internet and portrayed here.